You should group your source files by domain, then by feature, e.g. 'src/foo/model' and 'src/foo/exports'.
Is serialization/deserialization the only aim of these structures ?
If not, that code should definitely be separated, so as to evolve separately from the structure itself.
If it is the only aim, the code should also be separated, so you can change your serialization type (e.g. from JSON to XML) without impacting the model.
Also you might need another export for compatibility with another software, and you don't want your model file to grow with the 10 formats you support.