create:
heroku pg:backups:capture --app nameoftheapp
Starting backup of postgresql-dimensional-33144... done
Backing up DATABASE to b004... done
b004 represents the version of flatest backup for the app
download
# url
heroku pg:backups:url b004 --app nameoftheapp
#download to /tmp
cd /tmp
wget $(heroku pg:backups:url b004 --app nameoftheapp)