If you're using the bulti-in database locally there is a database viewer you can access to inspect the database. See instructions here: https://docs.mendix.com/howto/collaboration-requirements-management/sharing-the-development-database#5-start-the-database-viewer
What I tend to do is use Postgres locally and connect to a Postgres database in the configuration. That way I can use PgAdmin to inspect the database which is much nicer to use than the database viewer above. Details on adding a connection here: https://docs.mendix.com/refguide7/configuration#database