how can I turn off my firmware password to return my macbook air for services if I cant turn it on and I have already removed from find my?

Did you set up a Firmware password to begin with? If you did not then there is no firmware password to turn ON or OFF. The Firmware password has nothing to do with Find My.

If your MacBook Air every booted up and a screen with a white lock was presented to you then you have had a firmware password. If you have not set one then you do not have anything to turn OFF.

Axel F.