How to reset your tablet
If you cannot remember a PIN code, you may try performing a hard reset on the device by using these instructions:
1) Turn off the device.
2) Press and hold the Volume Up key and the Home key, then press and hold the Power key.
3) When the Samsung Galaxy Tab A logo screen displays, release all of the keys, then press and quickly release the Power key
4) "Installing System Update" will show for about 30-60 seconds, then a "No command" Android will appear before showing the Android system recovery menu options.
5) Press the Volume down key several times to highlight "wipe data / factory reset".
6) Press Power button to select
7) Press the Volume down key until "Yes -- delete all user data" is highlighted.
8) Press Power button to select and start the master reset.
9) When the master reset is complete, "Reboot system now" is highlighted.
10) Press the Power key to restart the device.