What size screws do I use to wall mount my SEIKI 40" TV

8/9

They are metric! Best thing to do is go to a hardware store and see about getting some samples that look close and try them.

Not sure what you are asking. Are you looking for the screw for the attaching the mount to the TV or the mount to the wall.
If you are looking for the screw size for the back of the TV, it could be metric size M6 or M8. Just be careful of the length. Too long and you will ruin the TV. Maybe google the TV model and it might show in the owner manual the exact screw to use.

the mounting bring the right screws for every sides

Bolt that works is an M5 16mm. Go to Ace...the helpful place. An M5 x 25 may or may not be too long. The 16mm was plenty long though.

Please look on the back, there should be 4 mounting holes (for Metric screws) Iin what is called VESA mounting pattern. Just measure the pattern.
http://en.wikipedia.org/wiki/Flat_Display_Mounting_Interface

When you buy the mounting bracket, it will come with a bag of Metric mounting screws to attach your TV to the bracket.

The size is #8-40 X 3/4". This is a specialty screw, so you're screwed

You can buy almost any wall mount for it, just be sure of 2 or 3 things... 1st the location, you have to screw some rather large bolts into the wooden studs in the wall so check where it will be located... 2nd weight and size... You want a mount that will be able to hold up the weigh of the TV, usually the size will be between 32" to 40" (various mount sizes) Just make sure the size 37" is between the size lengths... and 3rd that it has a "tilt" adjustment... due to the placement of the TV you might get either reflection off of a light source or you may need to change the angle so that you can see it better on the wall... Hope this helps out and if in doubt be sure to ask someone at the store you buy your equipment (TV, Audio, Games, etc)...

The screw holes are metric. The set is supplied with M5x25 screws to attach the pedestal, so the wall mount screws will be in that same range.