I have two Seagate 7200.7 drives which are natural SATA and Maxtor Maxline Plus II drive which is not a natural SATA drive.
When you're looking the drive from back, in the very left you see a wider thin black line, That's the SATA power plug. Very next to right you see narrower thin black line, that's the SATA data plug. Howewer, unless HDD manufacturer otherwise advises, it should be safe to use the molex plug in drives which are partially still PATA and not natural SATA drives.
Most today's power supplies have SATA power connectors, if not and you need to use SATA power plug, then use a converter.