I want to take a couple of extra controllers I have and make them usb. But a usb cord has 4 wires and these controllers have like 8 or something. I think my playstation controller has more.
Yeah, that's the easy way. You can get them for N64, SNES, NES, and some others, too. I've seen plans to build your own adaptors somewhere- Google is your friend (probably).
There are usb adapters but this is mainly going to be a fun project. That would take most of it out. It also would not help if the controllers were like xbox controllers. Same wires as a typical usb cable.