Hello Eyejon,
The included cables are useful for users who own PSUs that don't have the required PCIe cables. In your case, you have more than enough of them. So they are of no use to you. The Strix GTX 980 uses a 6 pin PCIe cable and a 8 pin PCIe cable. You can find a picture of how they look below.
Some users like to use a single cable to power their GPUs to keep the cable clutter down thus making their build look neater. Others use two separate cables. It's a matter of preference.
The included cables are useful for users who own PSUs that don't have the required PCIe cables. In your case, you have more than enough of them. So they are of no use to you. The Strix GTX 980 uses a 6 pin PCIe cable and a 8 pin PCIe cable. You can find a picture of how they look below.
Some users like to use a single cable to power their GPUs to keep the cable clutter down thus making their build look neater. Others use two separate cables. It's a matter of preference.
