Good day,
I left you two solution, found in a Google search:
Windows 10:
1.
Open Settings using [Win+I] keys
Click -> User account.
Here's shown, who's the administrator.
.
2.
Press Windows key + R
Write: Netplwiz
Next -> Enter
It will show you all the user and administrator account in that computer.
Best Regards,
Sincerely,
Jenny V.