Hi,
Just to set the expectations straight, this is a user-user support forum.
If you had a Windows 8.1 Retail license, the Pro upgrade pack also becomes retail and is transferrable.
You can move that Windows 10 license to a new Windows 11 machine. That is not an issue.
I hope you find this information useful. If you have any more questions, don't hesitate to reach out. Otherwise, please take a moment to accept the answer. Wishing you good luck!