Plugin help shopgui +

Hello everyone, I would like to help.
I use the shopgui+ plugin and the Vehicles plugin
I want to make people type /shop and then open the shopgui+ plugin and then add that people can buy Vehicles by the plugin ️Vehicles (No resourcepacks needed!)

Vehicles :

Anyone know how to do this, I would love any help.
have a nice day

If you are using other people’s plugins, you cannot customize their commands and items unless they allow you to from some kind of config.yml or something.