Ethernet for Latitude CPx

I just acquired a free Latitude CPx. I'm still figuring it out as the previous owner had NOTHING for it, and some parts no longer work due to a surge from a lighting storm (i.e. battery is dead, hard drive is gone, etc.).

I need to know what kind of card I have to get to hook ethernet up to this thing. It has 4 "slots" total: 2 large ones for batteries/CD-ROM trays, one for the hard drive and its tray, and then a 4th one. I'm assuming this 4th one is where things like an ethernet card would go, but I'm not sure what kind of slot it is.

I just want to be able to hook up ethernet to it. It can be wired or wireless, I'm not picky. I just don't want to pay a lot of money for whatever I end up getting.