You can use slmgr /xpr command to check if Windows 10 is activated.
You can also use commands to find the Windows Product key.
Option 1: run command prompt as admin. Enter this command:
wmic path softwarelicensingservice get OA3xOriginalProductKey
Option 2: Run PowerShell as admin. Enter this PowerShell command:
(Get-WmiObject -query ‘select * from SoftwareLicensingService’).OA3xOriginalProductKey