Hi muscle car,
your question is not about "how to make things bigger from the warehouse?". That means you are free to post your own new question by clicking the red "Post a Question" button! (Otherwise we only mess this topic up and won't be helpful for im60andprego's original problem.)

You can arrange cars by using the Move Tool .
If you don't mean "rigs" of "rods", but "Rigs of Rods (the game)" you should indicate that in your question and link to all relevant information that is needed to help you. SketchUp does not officially support this game, so you would have to go first to their website to look if it uses one of SketchUp's supported file formats. You would find that there is a program called "Editorizer". You would also find that there is a SketchUp Plugin that requires SketchUp 6.