The card requires 2 6pin PCIe power cables. If you don't have them you need to use the 4pin MOLEX to pcie adapter, or buy a new powersupply.
If you ahve no PCIe connectors there is a solid chance your PSU is not sufficient, check that it will provide enough power and be careful when using asdapters that you distribute them over the correct rails (if yuo cannot distribute them correctly you will need a new PSU).
The 4pin conector is either a molex (there are adapters for them) or if you are refering to the motherboard 4pin connection (looks like a pcie connector) that is for the motherboard only, not the PCIe.