Moving Adobe Acrobat to a New Laptop

I originally bought Adobe Acrobat 6 Standard many years ago. I bought an upgrade disc to Adobe Acrobat 9 Standard in Sept 2009. I am now changing to a new laptop and used the upgrade disc to install the software, however, it is also asking for the original product serial number from Version 6. I cant find that disc/box. Is there anyway to recover the original product serial number from my old PC or otherwise? I looked at my Adobe Account online and it only shows the upgrade. When I pull the program up on my old PC, it only shows the upgraded version as well.