Download Windows Server 2019 Evaluation from Microsoft
You click one of these links below:
This Windows Server 2019 iso file includes Windows Server 2019 Standard Evaluation and Windows Server 2019 Datacenter- Evaluation
How to convert Windows Server 2019 Standard Evaluation to Standard edition
Step 1: You open cmd (run as administrator), then you copy and paste this code
dism /online /get-targeteditions
You will see Windows Server 2019 editions you can upgrade
Step 2: You copy and paste this code in cmd
If you want to upgrade Windows Server 2019 Evaluation to Standard you copy and paste this code:
dism /online /set-edition:serverstandard /productkey:N69G4-B89J2-4G8F4-WWYCC-J464C /accepteula
If you want to upgrade Windows Server 2019 Evaluation to Datacenter you copy and paste this code:
dism /online /set-edition:serverdatacenter /productkey:WMDGN-G9PQG-XVVXX-R3X43-63DFG /accepteula
Done.