I would open the side panel to make sure, but I suspect those cables are supposed to be plugged into USB 3.0 jacks on the back, and lead to a USB 3.0 port on the front.
If the case comes with "USB 3.0" jacks on the front, but the motherboard doesn't have a header or the case doesn't have the fancy 3.0 connector for the internal header (It looks very different from what most people see on the outside of their rig), this is one way to get 3.0 on the front of your PC.