It's simple if you want backup ur data. You dont need a PIN for it:
1. Flash a STOCK ROM through ODIN.
2. Power ON ur device till the Bypass screenlock (wait 15 seconds).
3. Conect ur phone to the PC through the USB conector.
4. You will receive one popup window avising u what u wanna do. Select OPEN FOLDERS.
5. If you don't receive the popup is other thing. Having your device conected on Bypass Screenlock -> Press Windows Key + R in ur pc -> devmgmt.msc and press ENTER. Attach a screenshot and we take a look the yellow admirations you have there.