You'll need 2 cables plugged into the 5750. First the power connector will be from the power supply inside the case to a plug on the card inside the case. Make sure your PSU has a 6pin (listed as 2x3 PCIe sometimes) connector.
Second, you will still need a cable that goes from the back of your 5750 (where its outside the case) to the monitor. Check to see what cables come with the monitor and that you have the correct type of interface on the back of the card. Looks like most of them have HDMI, DVI, and multi port (not that common yet.)
All the data the 5750 needs will come from the slot it's plugged into on the mobo, so there's no cable between those parts.