is backup the data before you do anything to it. There's probably a Backup or Export option under a menu somewhere. That will make a copy of the data so that if you make a mistake you can recover using the data in that copy.
Anytime you're going to make a change (insert/update/delete/drop/alter) make sure that you can undo it by having a backup. If ever something goes wrong/unexpected happens, and it will, you will be glad to have the backup ready.
Backups are like toilet paper: lots is not a problem; not having enough is embarrasing...