Re:
Hello,
It won't work I'm afraid. You can only have one device connected to the cable modem, either by USB or ethernet.
Instead, connect all your computers to the router, then connect your router to the cable modem...after all, that is what the router is designed for.
Check to see if your router has a USB port on the back to connect a PC to it. If it doesn't and you only have ethernet ports, and your PC doesn't have an ethernet NIC, then you'll either have to buy a wireless network adaptor or buy and install a PCI ethernet NIC (which is a better idea, costing less since your router is nearby).