In general you'll need to convert the evaluation to full.
Dism /online /Set-Edition:ServerStandard /ProductKey:xxxxx-xxxxx-xxxxx-xxxxx-xxxxx /AcceptEula
above assumes a retail product key. If the key is volume or some other then as a work around, you can use a kms key as intermediary step.
Dism /online /Set-Edition:ServerStandard /ProductKey:VDYBN-27WPP-V4HQT-9VMD4-VMK7H /AcceptEula
then if successful use your own product key below after reboot
slmgr /ipk xxxxx-xxxxx-xxxxx-xxxxx-xxxxx slmgr /ato
--please don't forget to
Accept as answer if the reply is helpful--