Here all of the possible keypad combinations (video):

Or just read this lol

• Training 1 (door): 989
• Ep 1, Pt 3 (locker): 938
• Ep 1, Pt 5 (safe): 539, 541 or 584
• Ep 3, Pt1 (safe): 694
• Ep 4, Pt3 (door): 541
• Ep 5, Pt 2 (door): 415
• Ep 5, Pt 2 (safe): 919