Open the Registry Editor

Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp

Open PortNumber, switch to dezimal and change the port.

Click ok and close the registry editor.
By the way: U have to add a Firewall Rule for the new port to Windows Firewall…

I believe, following pictures are self explained…

now you have to restart the server or restart the “Remotedesktopservices” under the Windows Services but befor u test it: You should have physic access to the server, if something went wrong!
If you don’t have this option, install TeamViewer or something like that.. so u could return the changes in the registry.

If it works, deactivate the old RDP Firewall Rule in the Windows Firewall.