What options do I have for wireless for a power pc G5 to be able to access Airport Extreme??

I just got a new mac pro with airport extreme to handle the wireless needs. I have an old Power PC G5 1.8 GHz dual processor that I would like to use and have wireless capabilities. I want to use the airport extreme to access the internet on the power pc G5. I have an airport utility on the old power pc G5 but when I goto set up the airport utility, it states I do not have a wireless card. Where do I get a wireless card? Is there a usb I could hook up to function as a wireless card without needing to get into the computer. either option is possible, I just do not know how to move forward. Any help would be appreciated.