Correct, you cannot use the USB cable. Typically, the USB cable is usually only used for transferring of still photos. It is not supported by many (or any) camera soft video transfer to the Mac.
The appropriate Firewire cable should be in stock at any Apple dealer or at monoprice.com
There probably isn't any driver necessary - I don't have this camera, but if it is typical of most DV - Firewire camcorders, then iMovie will automatically recognize it.