Crap...
Crap...
You're working through a tricky setup process. To recover the Windows key, you might need to use a recovery media like Windows 10 installation CD or USB. For transferring files from the old computer, consider using a backup drive or cloud storage. If you're unsure, it's best to consult a tech support service.
The installation process should retrieve the necessary files. It might also access the Windows license registry using certain techniques (though I don’t have that expertise).