WiFi Adaptor for MacPro 3.1

The area in which I live now has free Wifi and I was wondering about the hardware needed to take advantage of this. I will need a WiFi adaptor of some sort either USB or PCI, so I am looking for advice on the best way to go, am thinking that an internal wifi card will probably not be strong enough, so some external device with aerial is probably best.

If anyone has any ideas I would very much like to hear from you.

Mac Pro 3.1 running El Capitan, and Sierra.