How to Recover deleted FB messages on iPhone 7/SE/6s/6s Plus/6 Plus/6/5s/5c/5
Note that this way is not available in the Facebook Official iOS 8 app, so you must log onto Facebook via PC. If you want to find deleted messages on Facebook without login, please skip to Way 2 directly.
Step 1: Login your Facebook via PC web browser like Safari, Chrome, etc. and navigate to Settings >> General >> Download a copy.