You need a screw extractor set. I have got one at Walmart on the tool aisle similar to this one. The hardware store probably has more of a selection. Make sure you get one with a screw small enough. You will need a drill and be able to follow instructions. There are more expensive ones called "speed out" that are easier to use, allegedly.
Black & Decker 16270 Screw Extractor Set, 5-Piece https://www.amazon.com/dp/B000KKR7JM/ref=cm_sw_r_cp_api_2PpPybYHB1QRX
If they are already stripped, you could use a screw extractor set.