How to load Windows licence into Mac?

I have Unity3d pro licence for windows and i want to use that windows licence in to Mac so how can i use it in my Mac.
I know that i can export my licence but the problem is that when i export my licence from windows machine it’s extension is .alf while my mac machine only accept .ulf. can anybody help me?

If you have a version of Unity that allows you to activate on two machines, then simply start the activation on the Mac, and enter your serial number. There is no need to export anything. If you continue to have problems, drop the support team an email, and let them know your serial number.