See also the official documentation:
Help Center > Members Manual > Working with databases > Exporting tables


How to export a database to a CSV or JSON file on your computer.

Open the database in question.  Go to the bottom of the page and select Export Table.  On the box that opens, choose either the JSON Format or CSV Format button.  You should get a popup from your browser allowing you to save or open the file.  Now you can do whatever you want with the information.

 

The official Groups.io user documentation is in the Groups.io Help Center.