Were can I buy a service repair manual on model 358.350870 18 inch bar I need to replace the fuel lines and fitting that goes in tank

no problem
you can get fuel lines from e bay that are generic and fit just about any unit
if yours has 2 lines you get the lines as a duel lines system including the rubber grommet for the tank
it will have either a walbro or zama carby and those workshop manual are available as pdf versions
Chinese carbies are knock of those makes so the manuals are applicable
if it under 100 cc then run the 14" bar but if over run the longer bar
siting unused for a period of time , will give you starting problems as the diaphragms dry out and will not work properly
Who makes it --any one guess it there is no other identification available

Fuel lines are generally fixed by replacement of the fuel line because the rubber it is made of deteriorates from age and alcohol contained in gas. Before you begin, make a mental note or take a picture of how the fuel line runs from the tank to the carburetor so you will be able to put the replacement in the same position.
On most chainsaws you need to take some wire, make a u-shaped end, which will be used to grab the fuel filter in the fuel tank. Drain the fuel in the tank. Disconnect the fuel line from the carburetor. Generally there are two lines on the carburetor, one for fuel, the other line creates suction used to pump fuel and is connected to the motor, not the fuel tank . Just disconnect the fuel line, it is usually on the side of the carburetor and will leak gas when disconnected. Once this is done, using the wire, gently grab and pull the filter towards the filler opening and using needle nose pliers grab the fuel line above the filter and pull. The problem you may have, is if the fuel line is in bad shape it will break, But once you have the filter off the fuel line, the fuel line can be pulled out from either the inside of the tank or from where it comes out of the tank and goes to the carburetor. Once it is removed you are ready to put the new fuel line in.
It is best to put the fuel filter on the fuel line next. It easier than trying to put it on inside of fuel tank going out. Spray some WD40 or equivalent, on the outside of the gas line, to help the line squeeze through the whole in the back of the tank, which it will have the go through. From the outside of the tank, where the fuel line comes out, fish some wire inside the tank and put the fuel line on the end of it, making sure not to pierce or damage the fuel line. If needed a piece of black tape will hold the wire better and help fit the line through outside hole. Once the fuel line is on the wire, pull it through carefully out the other side of the tank. It is best to use your fingers to pull the line through the outside hole, it makes it less likely the line will get torn or overstretched as line goes through the hole because of the extra rubber used on the line to seal the tank from inside and outside. Once the line is pulled through and seated, run the other end to the carburetor and you are done.

I am sorry we have no such diagrams, they are in the factory service and repair manuals and those are copy protected. You can buy access here www.alldatadiy.com for a fee.

The fuel line is replaceable by itself, you don't need a new tank. Just make sure you get the same size line or it will leak where it goes into the tank. Any local small engine repair shop should have the line. There are two lines that go into the tank, the pickup line has the filter on it. It not only filters the gas but keeps the end of the line down in the fuel.

Typical fuel line routing is:

One line (the one with the fuel filter in the end of it) comes out of the fuel tank and goes to the bottom fitting on the carburator. The second line comes out of the tank and goes to the bottom fitting on the primer bulb. The third section of line goes from the top fitting on primer bulb to top fitting on the carburator. Hope this helped and best wishes.

This is the typical fuel line routing on many models: One line ( the one with the fuel filter in the end of it) comes out of the fuel tank and goes to the lower port on the carburator. The second line goes from the fuel tank to the bottom fitting on the primer bulb. The third section goes from the top port on the primer bulb to the top port on the carburator. Hope this helps and best wishes.

The main fuel line goes to the bottom of the tank. The other, sometimes larger line goes to the primer bulb. This line goes just inside the tank, not more than 1"(inch).

Line from tank with the filter on it is the supply line and goes to the carb inlet fitting. This is typically on the "bottom" of the carb (with the tank being up) and will usually have a fitting with barbs or a bulge on it to ensure a tight fit. The other fitting on the carb is the return line and is usually a straight tube fitting with no barbs. That line goes the suction side of the primer bulb. The third line goes from the outlet of the primer bulb to the return barb fitting in the bottom of the tank. Fittings have to be removed from tank to properly install the new hoses on them. Remove retainer ring on outide of tank and push fittings into tank, then shake out of the fill opening. More details on replacing hoses are listed in another post about Repairing Ryobi trimmer.

To leemineres, if hoses are on right and unit still stalls after starting initially you probably need to disassemble carb and clean out using spray carb cleaner. May be sticky needle valve, or partially plugged port or jet.Could also be hole in diaphragm. Gasket and diaphragm kit would be good to add when you take apart, even if diaphragm does not have a hole.