Are you referring to the Passcode that is used to unlock the iPhone to get to the Home Screen? This passcode should have been reset along with your iPhone when you Erased all contents and settings on your iPhone. Did you use the process below? Please review the process below and if have not used it then try it:
You will need to reset the passcode on the iPhone. You will need a computer to complete this task. You can reset your passcode by following the instructions in this article by Apple ➔ How to reset your passcode on a disabled iPhone. All your data on your iPhone will be wiped clean in the process.
If you have a backup created then you can ➔ Restore Your iPhone from that backup file. If you do not have a backup file created then you will lose all your data on the iPhone.
If Photos, Messages and Contacts are synced to iCloud then you will be able to retrieve them after setting up iCloud on your iPhone after you reset the passcode and sign into iCloud.
Axel F.