Activation code

I am new here and need to ask a question which has probably been asked a hundred times before. I have been using Cubase vst 5 for years with no problems. My PC packed up so I bought a Macbook Pro. I know my software will not work on a Mac so I bought a laptop PC and installed my software. Then I find my dongle has nowhere to plug in and I need to buy a USB e licenser, which I have done. Now I need an activation code……hence my question ….how and where do I get one as I only have a serial number on my original software. Thanks, Peter