How do I connect a product like this to my fans? That's where I'm stuck. I see 3 pins coming out for each fan but I have fans with 4-pin Molex connectors..
-snip-
See the plastic part below the pins?
That's what you should follow, your fans' connector should have a specific space where that part fits,
so even if the 4th pin isn't available, as long as the other three are in position, the fans will work.
The fourth pin (
control) is for speed control, the third (
sense) is for speed detection, but that device itself has a speed control switch so the fourth pin isn't necessary.