From following guides on prism and reading the manual it seems the general process is to create a module with views, viewmodels and models. Then hook the view up with the viewmodel and use the view model to interact with the model.
However I have a model data structure that needs to be used across multiple different modules. Say, this model is called Car. And I have 3 modules, ModuleA, ModuleB and ModuleC that all need to use Car. If it was just used in ModuleA I would obviously put it in the Model folder of ModuleA. But as it is used in several modules, where do I put Car?