you have installed windows server evaluation version and now you want to change it to full version.
with the following command you can run an upgrade.
open command line as administrator and run the following command:
DISM /online /Set-Edition:ServerDatacenter /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEula
update your product key and your server version then run this command.
when finished you will need to reset the server
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