I have a backup of my iPhone 5 on my computer and I had a security code that I know I used but as I just got a new iPhone 6S, the backup is not working as it is stating the security number I am putting in is wrong so is there a way around this or a way to reset the code of the backup that I no longer have the phone? I need this backup and I can't get into it....help! Thanks.
Unfortunately there is no way to access a password protected backup without having the correct password (passwords are there for a reason). You can check if you have an iCloud backup available from your iPhone 5, but as far as the iTunes backup you won't be able to access it until you enter the correct password.
Apple specifically mentions that "There is no way to recover your information or turn off Encrypt Backup if you lose or forget the password", so you just might be out of luck on this one.
This page might help, good luck.