/system backup save name="filename"

/tool fetch address="ftpaddress" src-path="filename.backup" \
user="ftpuser" mode=ftp password="ftppassword" \
dst-path="Path of your ftp(/Mt-Backup/filename.backup)<--example" upload=yes

delay 10;
/file remove filename.backup

Enjoy!

Thank you very much, it has been great!
Any way to put a key to the backup?
Thank you.