Here is a link to an article describing how to extract your product key using the software "ProduKey". I don't know if Microsoft has a record of who they originally sold Product Keys to, but if you contact them, they would probably be interested in the Product Key on your computer:
http

/www.techadvisor.co.uk/how-to/windows/how-find-windows-10-product-key-3632749/
I can't vouch for the software, I just learned about it from the linked article. Perhaps there are other ways to extract the product key.