Intel i3 2120 pros Intel dh61ww mother board 4gb ddr3 ram Intex 500 w psu I want to kow Best gaming graphic card

Solution
Since the board has a PCIe x16 slot, a GTX 750Ti or RX460 depends on their pricing where you are would be the best performing cards for your configuration.

Make sure to see if your PSU has the PCIe 6pin power plug (I'm not recommending that PSU, just showing you a link to see what that plug look like) that some models of these two cards may require.

FD2Raptor

Admirable
Since the board has a PCIe x16 slot, a GTX 750Ti or RX460 depends on their pricing where you are would be the best performing cards for your configuration.

Make sure to see if your PSU has the PCIe 6pin power plug (I'm not recommending that PSU, just showing you a link to see what that plug look like) that some models of these two cards may require.
 
Solution

FD2Raptor

Admirable
If you were saying that your PSU has the ATX 20+4pin then every PSU has that plug nowadays; it's the PCI-E 6/6+2 pins plug that you should be looking for on your PSU, and yes this mean I'm telling you to unplug your PC from the power socket, open your case, then using your eyes to check if your PSU has that plug or not; while you're at it, note the number of Amperes the PSU has on its 12V rail. For the GTX750Ti the 12V rail should have at least 20amps on it.