Q: my bluetooth keyboard is not being recognized with the right keys

I just had my iMac serviced at the local Apple store and the wiped it clean and reload the operating system.  I:m now trying to set up the iMac and its not recognizing the bluetooth keyboard correctly.  I tried looking for the right key layout in the preference section but did:t see one with my keyboard layout.  My keyboard is about 2 ' 1/2 years old and has the @ key above the 2 key where the iMac has set the keyboard up to have " above the 2 key and @ is to the right of my P key which should be the [ key.  How do I get my iMac to recognize the right keyboard layout?

Thanks