First, you have to match the voltage and curent type(AC or DC) of the fan to your power source. Your picture looks like a computer power supply fan, which I think runs on 110v AC. If that is right, take the fan to a hardware store or a GOOD auto parts store and find crip in female spade connectors that will fit the terminals. Then buy an inexpesive extension cord, cut the female end (the one that things plug into) off and either strip the wires back far enough to reach through the crimp connector and crimp the ends on ( if oyu don't have a set of crimping pliers and/or don't understand what I'm talking about, just get someone to crimp them on for you) and plug them on to the fan, plug the cord in and check that the fan runs. Then mount it over your hole in the cabinet and you should be good to go.
Good luck. You've got a great box going there. Congratulations again.
Don Jones