this is what you currently have HG2F3 [IMAGE] you can get a Dell proprietary sata power cable that has > 2 standard sata power connectors.  Dell Optiplex 3040 5040 7040 HDD & ODD SATA Power Cable 7G26H [IMAGE]   only $5.45 [URL]    
I have an Optiplex 5040 SFF with the standard board power cable HG2F3 for one HD and Optical drive. My board has two SATA ports and room for another Hard Drive. Unfortunately, the HG2F3 power cable only has one HD connector, Is their another OEM power cable that will accommodate two Hard Drives?
Internal Power connector