If you can't remember it then you'll have to do a data reset through recovery mode.
There is no way to back data without getting past the lock screen.
If you've set to Google or Samsung Account then it may have backed up data automatically but cant be guaranteed.
You'll need to plug into Laptop/PC and press and hold volume down button and power button, for about 15 seconds, until phone boots down. As soon as it boots down change to volume up and power and keep holding until it goes into recovery mode.
If unable to get into it, you can call Samsung Support for a repair. It'll be charged as it's not a manufacturing defect.
