(https://s22.postimg.cc/9qojp5f2l/PCIe_to_Molex.jpg) (https://postimg.cc/image/9qojp5f2l/)
With the locking pin facing up on the PCIe connector all three pins are negative the two bottom pins are 12volts on each corner.
(https://s22.postimg.cc/tflnt9p7x/4pinto_6_pin_pci_express.jpg) (https://postimg.cc/image/tflnt9p7x/)