HeHe...I did the samething to my older rig. I salvaged a Delta 120mm fan (89cfm, 45dba) and it to had a 2pin power connection. I searched and couldn't find a 3-2pin adapter. So I tested the 2pins (red, black) to be positive and negative. I then attached it to a 3pin to 4pin (recommend 3pin to 4pin because you don't want to plug it in the MB if you don't know how much juice it's pulling) adapter. Man does this thing move air. So just get a 3pin to 4pin adapter. Make sure you connect the positive side to the adapters positive side (red on red, black on black, etc.). I just push it down on the 2pins allowing the white plastic on the mail 3pin adapter to flex a little.
Have you found out the cfm/dba of these fans? Mine was from a mainframe powersupply unit.
-JC