Well it depends on if you want it to run at full speed or not... I just rolled the two red wires and two black wires from the fans together and then taped each set to the corresponding end of the 9v cellphone plugin adapter wires.
12v would be full power, which equals full speed.
9v will give it like 8/10ths power,
and degrades from there.
You have a small box though, so you gotta decide whether or not they're going to be pulling and pushing enough air into your environment. Two fans is all I have for a computer case grow, so you may want more. Also, you have that little fan mounted in there, that'll work as an exhaust as well, if you have the top on and it's sealed or close to it. Smoke On.
Did you get the green bulb?