Upgrade Windows Server  Evaluation to Standard edition. which is fortunately very easy!

First open up a Powershell window and run as Administrator.

Enter the following command:

DISM /Online /Set-Edition:ServerStandard /ProductKey:xxxx-xxxx-xxxx-xxxx-xxxx /AcceptEula

DISM will proceed to make the required changes and will request a reboot. Press Y to reboot the server.

Once the server has rebooted, log back in and open up Powershell again and type:

DISM /Online /Get-CurrentEdition

Congratulations you now have standard edition installed!