You have to look that up, by the looks of it your board is a SATA board, so you buy a PSU what has SATA connectors 
Pinouts will also matter. He needs to know if his motherboard has a 20 or 24 pin plug, and whether it is ATX standard or proprietary. Also, the video card may need an external power source, so the power supply will need an available matching plug for that.
Lastly, reliability with power supplies is major. You'll want one with decent, stable rails on it, which has a high enough wattage rating to output more power than your computer needs at peak usage.
Another big thing to not forget: Computers get hot. Make sure your existing/desired cooling system can handle the new video card and power supply without things getting too toasty.