That looks plenty sufficient to split your single Molex (4 pin flat) connector into 2 or more. One caveat however... you don't want to overload the wire size that the original Molex is fed with. I can't see that happening with 2, 3, or even 4 drives. But don't add more devices to the Molex chain than you need. I believe most HDDs draw about 1.5 - 2 A at start up
and much less when running.