External HDD to Airport Extreme

Hi, I have an airport extreme attached to my router and would like to start using Time machine wirelessly after setup, I've seen a G-Technology G-drive mobile portable HD at the apple store and wanted to know if this could be used as a permanent external HD, it only has a USB 3.0 input, no power, firewire or ethernet facility.

Could I attach it to my macbook pro and setup Time Machine for the first time then plug it into the usb port on the extreme to update wirelessly.

Thanks for any help

Peter