If there was an install of Win 10 on that motherboard, you can always reinstall win 10 on it again - unless you link it to an email address or used a login in last 2 years that is linked to an email address, as then the install might be linked to that email address, and not motherboard - you can login to your account on Microsoft web site and check what devices linked there.
If its still attached to motherboard, all you need to do is download the
Windows 10 media creation tool and use it to make a win 10 installer on USB, and install win 10 on hdd,
when you reach the screen asking for licence, click "I don't have a key" and win 10 will continue to install and reactivate once finished