Alright, what you need is one 6 pin connector, and one 8 pin connector.
so first find the a 6 pin cable, and connect it to the 6pin connection, then find another 6 pin cable, and one 2 pin extension( which equals 8) and connect it into 8 pin connection
http://techreport.com/r.x/psus-0907/pcie-connectors.jpg
look in the picture, those are the cables you are looking for.