My AC wont blow cold. As soon as I put freon in it, it blows cold for about an hour, then hot again. My friend told me that the orifice tube in his car needed to be replaced because it was convertine the freon, which is a gas, into air. He said that replacing the orifice tube would fix the problem. I just don't know exactly where to locate this tube on my 2009 Chevrolet Cobalt.

Sounds like you might have a leak. If you charge the system and works for a time ,(hour, week, year) and then quits it sounds like perhaps the freon is leaking out somewhere. Freon does not ever get converted to air. Freon is in several states of existance while it is in your system. It is a high presure liquid, high presure gas, low presure liquid, and a low presure gas, but it is still always freon.
The valve your friend is talking about is called an expansion valve. What it does is to take the high presure "liquid" freon and allows it to pass into a low presure zone called an evaporator at a regulated rate. When you take freon at a liquid state high presure condition and expose it to a low presure environment it "evaporates" ( thus the name evaporator) and it gets very cold when it does this. This is where the cold air you feel coming out of the vents is made.
But the freon is in an enclosed system. By this, I mean it is never exposed to air, moisure (water), or anything else. I goes through all of these changes while inside this enclosed system.
Therefore, if the enclosed system is good then the amount of freon inside it will not change. If the amount of freon doesn't change then adding more will only make things worse.
I would suggest having the system checked with a hologen leak detector and/or system dye to find the leaks. Remember, if you have to add freon, then the freon that was there before must have escaped from somewhere.
Find a reputable shop to check the system for leaks. If it is leaking bad enough to run low in a hour it should be an easy to find leak.