Converting pro license for Unity 2.6.1 to Unity3.1

Sorry, can someone please tell me how to convert the pro license for Unity 2.6.1 to Unity 3.1?

Do we have to send them a message and pray they return a mail with the new code? Or is there an option I'm not seeing here?

Thanks!

It's not possible. You can go here and buy an upgrade though, which gives you a new license specific to Unity 3.