this is a guess, but my assumption is the "correct" way to connect that adapter you have is via connecting the two molex together (right, they mate?) then connecting the 3 pin header to the motherboard, then connecting the pump's 1 pin female plug to the adapter's 1 pin male plug.
if that'll actually make it work how you want? I have no clue, but that's how that adapter is supposed to work I think.
dmm - digital multi meter = voltage reader thing.
rinse repeat = i'm not sure which exact term your bios will use, so you may need to cycle thru the settings to figure out which one drops voltage below 12v, that isn't pulse width modulated.
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