Mine is located here, as also mentioned in the article: “Open a new Finder window, then tap Command+Shift+G. Enter this in the box that pops up ~/Library/Application Support/MobileSync/ then find the folder named “Backup.””

My iTunes folder is on an external drive, but it still backs up to my laptop when I connect my phone. Are you sure your phone backups are on your external hard drive instead? Please let me know if you have a solution around that.

This didn’t work for me. I did everything as written, but it still creates a new Backup folder at this location: ~/Library/Application Support/MobileSync/ when I open i-Tunes and tries to back up on my laptop instead of the external hard drive. Do you have any suggestions?