How will i know will this graphics card will fit on my motherboard

What is your motherboard?

wait i let me check

There's a few ways to check... easiest is probably just to download CPU-z (google it), run it, and click the "mainboard" tab. That will tell you the make and model of your motherboard.

my mother board is MODEL G31-M7 TE

http://www.biostar.com.tw/app/en/mb/introduction.php?S_...

There's the website for your board.

That probably has a PCI-e 1.0 or 1.1 slot on it (not sure). So, it will work with any modern graphics card, but I would recommend pairing it with a lower end one (in the $100-150 range) just so that it doesn't get bottlenecked by PCI-e bandwidth or by your CPU.

Can you give me a specific graphics card name so that i can look for it?

Well I'm not sure exactly what you are looking for but if that were my system I would probably pick up a Radeon 6770.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

It would be helpfull if you told us the rest of your spec, though I think your safe with the 6670 but really depend on what you are trying to do. I mean are you just replacing an old card or trying to play games etc. we would need to know what the rest of your system looks like (at least what he psu is rated at).

i m trying to play games counter strike source and other fps games

CS:S will do just fine on a 6770

Thank you. Your information helped.