Windows Server 2016 Evaluation To Standard -
DISM /online /Set-Edition:ServerStandard /ProductKey:WC2BQ-8NRM3-FDDYY-2BFGV-KHKQY /AcceptEula Once the command succeeds, reboot:
slmgr /ipk YOUR-NEW-PRODUCT-KEY slmgr /ato Run: windows server 2016 evaluation to standard
DISM /online /Get-TargetEditions You should see "ServerStandard" listed. windows server 2016 evaluation to standard
shutdown /r /t 0 After rebooting, open Command Prompt (Admin) and set your KMS server or enter a new key: windows server 2016 evaluation to standard
DISM /online /Set-Edition:ServerStandard /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEula Replace XXXXX-XXXXX-XXXXX-XXXXX-XXXXX with a valid Standard edition product key (Retail or MAK). A generic KMS client key will not work for this retail conversion. If you do not have a retail key, you must use the Volume/LTSC method (Step 3b).
Here is the text for converting a Windows Server 2016 Evaluation copy to a full Standard edition.