Sorry for the delay in responding.
I am backing up as follows, using a Cron.
mongodump -d DBNAME --gzip --archive=/www/backup/database/mongodb/DBNAME-date "+%Y-%m-%d"
.gz ; find /www/backup/database/mongodb/ -type f -mtime 7 -exec rm -rf {} \;
That way, it backs up the day, and deletes backups older than 7 days.
I hope that soon aaPanel will have this in its automatic backup cron