Recover notes from old backup

Hello! Can anyone help me figure out how to recover notes from a previous iphone backup? I deleted an old work email from my iphone 4 without realizing that all of my notes were attached to that account and not my personal one. I did backup my phone regurlarly and also backed it up again after deleting the account, before I realized that my notes were gone. I have asked and my old employer will not re-activate the account for me to recover the notes and I've looked in itunes but the only backup I can find is the most current one without the notes. Also, these notes are not on my icloud. I don't have any additional software- only itunes and pc to search. Anyone know how to locate and recover notes in a previous backup? I know what day I need to go back to, but when I search there are a bunch of different files and everything I click on says that I don't have the right program to open it. Obviously I'm not the most iphone savvy, so any help and specific instruction for how to do things would be greatly appreciated!

Thanks so much!