Windows 10 Pro: VK7JG-NPHTM-C97JM-9MPGT-3V66T
Everybody gets the same product key (depending on version) from an upgrade. If you switch motherboards, you will have two options:
1. Reinstall Windows 7, 8 or 8.1 and upgrade again to Windows 10
2. Call Microsoft and beg them to activate your Windows 10 for you.