Power supply for Sata Hard Drives?

I have 3 WD Serial ATA hard drives and every one of them has a special power supply connection but also what looks to be a standard power supply conection, or at least a standard power supply 4 pin conector will conet to it.

My P S U Has 2 Serial ATA conectors, could I use one of the standard conectors on the standard side of a sata drive if I want to add a 3rd or do I need the converter?

Use the SATA connector for the SATA drive if you can, but molex is just fine.