Hi @Sere ,
SQL server Enterprise evaluation is free edition, but it will expire after the 180 days.
You can upgrade SQL server evaluation to SQL server standard edition.
It seems you bought MS SQL Standard volume license, the key is imbedded in the product, you can try the solution from the blog Upgrading SQL Evaluation to Volume License. Get Microsoft Volume License key then upgrade your SQL server. Run your SQL server setup file, select Maintenance and click on Edition Upgrade. Enter your standard Volume license key.
If you already have SQL server standard license key, Please follow the steps from the blog How to upgrade SQL Server 2012 Evaluation Edition to Standard or Enterprise.
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