Retrieve Passcode from iphone backup files

This is the scenario in front of me.

An iPhone 4s is available with enter passcode. I have its backup taken from iTunes. I have extracted all the files (*.plist, *.db, *.sqlite, etc.) from those backup files.

Now my job is find the passcode from the backup. I no longer have access to the iPhone.

I have viewed almost all the files and still unknown with the file that contains the passcode. It would be great help if anyone would point me into the right direction.

If any other security app such as Applock is present, where does its passcode resides.