How to Transfer an iPhone Backup From One Computer to Anotherby Bennett Gavrish
Every time you connect your iPhone to your Mac or Windows computer and sync the device, iTunes creates a backup of your phone's data and stores it on your local hard drive. If you are switching to a new computer, you may want to transfer your iPhone backups along with the rest of your data. That way, you can sync with iTunes on the new computer and revert to an old backup if your phone encounters a problem.
Connect a flash drive or external hard drive to your old computer.
Click on the "Finder" icon and navigate to the "Macintosh HD/Library/Application Support/MobileSync/Backup" folder if you are Mac user. If you are a Windows user, open the Start menu, click on "Computer" and then navigate to the "C:\Users\user\AppData\Roaming\Apple Computer\MobileSync\Backup" directory.
Select all backups by holding down the "Command-A" keys if you are on a Mac. In Windows, press "Ctrl-A."
Drag and drop all of the backup folders to your flash drive or external hard drive.
Eject your flash drive or external hard drive and plug it in to your new computer.
Repeat Step 2 on your new computer and then drag the backup folders from your flash drive or external hard drive to the "Backup" directory on your new computer.