If you don't have a Product Key or Windows 10 license, you can go and buy Windows 10 Pro from the Windows Store.
The Windows 10 Pro Steps as fallowing,
Go to Start button, select Settings Option >> select Update & Security >> Click Activation Option and final Go to Store.
You can use the Windows 10 Pro Default key.
Default key: VK7JG-NPHTM-C97JM-9MPGT-3V66T
This default key will not activate the system; just take you to Pro so you can activate using a valid Pro key that you will provide.
For more detail go to links,
Thank you! I hove it might help you!