use Show Key Plus to find your product key - see instructions:
How to Find Your Product Key After Upgrading to Windows 10
http://www.groovypost.com/howto/find-windows-pr...
After downloading it, extract the zip file then launch ShowKeyPlus.exe.
ShowKeyPlus will reveal your product key and license information such as:
Product Name
Product ID
The currently installed key, which is the generic product key used by Windows 10 depending on the edition installed.
The Original product key. This can be your Windows 7 or Windows 8 retail or OEM product key before upgrading. This is the product key you want if you encounter product activation issues in Windows 10.
OEM Key OR Retail: ShowKeyPlus will check for the presence of an OEM marker; that is how big name vendors activate multiple machines at the factory running Windows.