My best guess is something like the following:
- Export all your tables from Airtable in CSV format.
- Massage all the CSV files in Excel to match up with the database schema of your new database.
- Use the standard import tools of your database to import the CSV files.
I’m assuming that most of your 19 GB is attachments. Storing binary “blobs” in your database is an entirely different topic and an art unto itself, and the best solution will depend on the database system you choose. One of the most popular strategies these days is to store those large files in something like AWS and just keep the URL to the file in your database. It all depends on what type of data you’re storing. The AWS approach integrates with various caching/CDN services too which is great if the people who need to access the information are widely distributed.
Good luck with your project.