This guide does show you how to perform a factory data reset on a Galaxy phone. Before you do the reset, know that ALL of your data will be completely erased.
Samsung Galaxy Tab A (T387AA) - Reset Device - AT&T
Manage files on your Galaxy phone or tablet
How to perform Factory reset on your Galaxy phone
How to reset a Samsung Galaxy tablet
Hard Reset vs. Factory Reset: What's The Difference?
Screen mirroring to your Samsung TV
Samsung Galaxy Tab S6 - Factory Data Reset (Powered Off)
Manage files on your Galaxy phone or tablet
How to Perform a Factory Reset on Your Android Phone or Tablet
Samsung Galaxy S8 / S8+ - Factory Data Reset (Powered Off)
Different ways to restart your Galaxy phone or tablet