Microsoft does not appear to provide a public way to verify Windows activation status from a key serial number, and Microsoft Support normally would not confirm whether a specific OEM key has been activated just from a serial number.
But you should be able to verify it by doing this:
Launch Powershell (note, it is not Command Prompt, but Powershell), and run this code to see if you have an OEM license on the motherboard.
(Get-CimInstance -ClassName SoftwareLicensingService -Property OA3xOriginalProductKey).OA3xOriginalProductKey
If it return no key, then it means there's no OEM license installed at all in the firmware/motherboard.