If you are getting the message "No hardware Installed" it means that macOS is not detecting your WiFi adapter for one of two reasons:
- It's not installed (it physically doesn't exist)
- It has failed
Chances are it's the second option.
You can confirm this by running Apple Hardware Test (AHT). Hold the D key while booting from a powered off state with the AC adapter connected.
Regardless if the first or the second, you will probably have to replace it with another Airport card
ifixit.com has an excellent tutorial and step-by-step guide on how to replace the board. It's a time consuming repair - I wouldn't say difficult, but more detail oriented. If this is not your cup of tea, I recommend taking it in for service.