Usually most companies state their organizational structure type in one of their documents, which means that you can ask just any project manager/functional manager and he will tell you the org structure type of his company.
If this is not the case (or you can't ask anyone in the company), then your best bet is to check the organizational hierarchy in the company.
If you also don't have access to the organizational hierarchy document of the company, then you should check how the reporting is done: Does the PM report to the functional manager? You also should check who has authority over who: Does the project manager have authority over his team members? Or not?