Here's a neat trick I discovered the other day that I guess will help you accomplish what you are trying to do by finding out where the backup folder is located.
I was having this same issue until I found advice on how to find it.
The Library folder that you need to access is NOT
Macintosh HD/Library/Application Support
This is what i was doing when looking for it and there is no Mobile Sync folder in here.
What you need to do is when you have Finder open (desktop view), in the Finder menu click Go>Go to Folder then type or copy/paste:
~/Library/Application Support/MobileSync
and it will open the correct folder. The Library folder may be hidden for whatever reason when searching in spotlight, but when you access the folder this way it will appear. Hope this helps. Here is where i found this information. https://discussions.apple.com/thread/3481349?start=15&tstart=0