This installation steps are applicable for the OpenCart versions 3.0.x.x

1. Login to your website Admin
2. Go to Extensions > Installer
3. Click on upload and upload pro-order-id-lite.ocmod.zip
4. Go to Extensions > Extensions. Choose Modules from the drop-down
5. Look for ORDER ID SETUP (Lite) in the modules list and click on Install.
6. Edit the module and setup.