Hello @Robert Anton ,
SQL server does not store license information inside SQL Server at all. You need to check your license paper or the proof of purchase by yourself.
Suggest you contacting a Microsoft sales partner or licensing expert directly. Call (1-800-426-9400), Monday through Friday, 6:00 AM to 6:00 PM PST to speak directly to Microsoft licensing specialist. Or you can go to Volume Licensing Support Contact support. Please choose region/language and call. People there will help you more effectively.
Or you may try the Powershell written by Jakob Bindslet in this thread to get Back the SQL Server Product Key Information from registry, but there is no guarantee, and you have to modify the location of registry to match your SQL Server version.
Best regards,
Cathy