Change Device Backup Drive Location in iTunes

Hi I tried the MKLINK advise in the previous discussions at The Complete Guide to Creating Symbolic Links (aka Symlinks) on Windows, but it still showing " Cannot create a file when that file already exists." What's wrong with my command? Can anyone help? Thanks.

Here is the commands I wrote:

C:\WINDOWS\system32>MKLINK/J "C:\Users\Christine Souso\AppData\Roaming\Apple Computer\MobileSync\Backup" "E:\MobileSync\Backup"

當檔案已存在時，無法建立該檔案。translation>>> (Cannot create a file when that file already exists.)