1. Install “Virtual Machine Manager” (VMM)
2. Create an ubuntu VM in it
3. Bash in ubuntu, mount a share from NAS share folder:

// /backups        cifs    username=<backup_user_name>,password=<backup_user_password>,iocharset=utf8,sec=ntlm,vers=1.0  0  0

Make sure your mount point (/backups in this case) exists before you do it.

4. Setup rsync command:
Since NAS share folder has different permission model with Linux, this command will work:

rsync -rvh --size-only --progress --delete --password-file=<path_to_password_file> <username>@<server_host>::<folder> ./<folder> --port <port> --exclude-from=exclude.txt

5. Add rsync command into crontab to run it automatically.