Greetings!
This is Tin, I'll do my best to help. Looks like you're trying to find the Windows Product key that you've purchased from MS Store.
Usually you will only get the Digital license which be associated with your MS Account. So when you wanted to use your license, all you have to do is to sign in your account and it should be activated.
To check it, please click Start menu and type Activation then hit enter. You'll see there that it is activated with digital license.
Thank you,
Tin