You will need a new server with a fresh install of Unbutu 16.04 - 18.04. You will then want to SSH to the server and run the following commands.
git clone https://github.com/poppabear8883/UNIT3D-INSTALLER.git installer cd installer sudo ./install.sh
All credits to poppabear8883 for this wonderful installer.
For more info please visit https://github.com/poppabear8883/UNIT3D-INSTALLER