The PowerMac and iMac G5 are two different types of machines. Please go here and see if it is the first link or one from the second link.
https://everymac.com/systems/apple/imac/...
https://everymac.com/systems/apple/power...
Is this the antennae you used?
http://www.macpartsdepot.com/922-6043-ai...
Which airport did you use:
airport extreme card
UPDATE
I’ve updated your icon and question description
FYI here’s the Bluetooth module
https://www.macpartsdepot.com/603-3421-9...
This model used the Apple part# 661-3045
http://www.powerbookmedic.com/parts/661-...
Here’s a video on how to install the card. Be sure to plug the antennae cable into it!
https://www.youtube.com/watch?v=gVGOpCST...
Now go to your System Preferences and make sure it sees it and is turned on.