We created a quick guide to backing up your Airtable bases.
The most basic way is to set a regular time in your calendar every week and export each table in your base.
If you need an automatic backup option with attachments included, try the On2Air: Backups solution. You can set backups to run on a schedule and automatically be uploaded to online storage.
(plus, you get access to the other useful On2Air apps - you can try it out with the free trial)