See: How to Deactivate Facebook Account Temporarily
Step 1: Login your Facebook via PC web-browser like Safari, Google Chrome, etc. and navigate to Settings >> General >> Download a copy.
Step 2: Click on "Download a copy" button and click "Start My Archive" afterwards. Then you'll receive an email to verify your Facebook identity. After that head for mail inbox and click on the given link to start downloading Archive file.
This article was first made public on Learn Facebook basics at this URL here.
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