Hello,
Could you please confirm whether you are referring to the Windows Product Key used for activation or the Device ID?
If you are looking for the device ID (unique identification number assigned to your device), go to Start > Settings > System > About > Device info.
However, the product key is different and is used to activate your Windows edition.
If the product key is preinstalled with your device (OEM) Motherboard, run the command below in Terminal (Admin) to locate the 25-character product key.
(Get-WmiObject -query 'select * from SoftwareLicensingService').OA3xOriginalProductKey
You should be able to see the product key installed on your device.