What you want is quite difficult, because you miss a bunch of information that's needed to recreate the domain model. For instance, let's say you have a join table (with two foreign keys to two other tables). How do we know which tables are referred to? Is the relationship mutual or only readable from one side? Etc etc.
I'd suggest you write a converter that either imports all the data via a java action or via webservices.
If it is a older mendix project database, you could just open your project in mendix. Choose for multideveloper project and open it.