USB connector = USB adapter???
Not much difference between pci or usb adapters (which receive the wireless signal from router). Usb adapters are slightly more expensive but dont require internal fitting and can be swapped to other pc's. Advantage of pci is they dont use up a precious usb socket, but, if you were short of pci slots...........
Commonest mistake is to buy the wrong router for your connection. If your modem plugs into a usb socket then your wireless router needs to be usb not ethernet which adds to the confusion.
So, does your modem connect to a usb socket?