Question about Delock 6Pin to 2x 8Pin for graphics card

The GTX750 requires an 8-pin power connector.

If your power supply is modular, it should already have this cable. Otherwise, graphics cards should come with an 8-pin molex adapter, like this one:

Delock 2x Molex to 8Pin Graphics Card Power Adapter, 15cm

If you don't have this adapter, you can use the one mentioned above.

The GTX750 does not need an external power supply, so you don't need this cable.