Extract the file to get the Base and Def mods.
Special Transport Pick-Up Truck Skinable for American Truck Simulator
It only works with Special Transport DLC which is required and can be seen in traffic or at various road events.
Create your own using the below link:
https://steamcommunity.com/sharedfiles/filedetails/?id=1687265762
https://steamcommunity.com/sharedfiles/filedetails/?id=1687265762