hehe, mouser's website is awful - use their catalog if you like to purchase from Mouser
Molex KK is a BIG family, you have polarized, non polarized, friction lock, locking tab, and then different numbers of circuits, rows, current ratings, coating types, the list goes on
the easy way would be buying from reseller that offers a small selection (like futurlec or jameco), or getting a print catalog, so you can see the specs for the different model numbers in the KK family.
alternately, you can visit the Molex website, which has a handy search by picture feature, to identify the exact part you need.