If you have already deployed a server using the evaluation ISO and realized your mistake later, you do not need to format the machine. You can convert the operating system directly to the full retail/volume edition using DISM. Step 1: Check your current edition
If you have a developer subscription, you can find non-evaluation ISOs under the downloads section of the Visual Studio portal Microsoft 365 Admin Center: Windows Server 2016 Standard Iso Not Evaluation
Complete Guide to Downloading and Activating the Full Windows Server 2016 Standard ISO (Non-Evaluation) If you have already deployed a server using