While the built-in Trainz Content Manager handles these files perfectly inside the game, creators and modders frequently need a to extract raw data, modify textures, tweak configurations, or convert assets for use in other 3D modeling programs.
Several community-developed and official tools are commonly used to manage and "convert" these files: CDP Explorer trainz cdp converter
For most users, the standard way to "convert" or manage these files is through the built-in Trainz Content Manager convert CDP file so I can open it in Blender - Trainz While the built-in Trainz Content Manager handles these
If you need an created from this content, you can: trainz cdp converter
If the goal is to extract the raw files (meshes/textures) for editing without installing them into the game database: