For lazy people like me, i use mongodump it's faster:
mongodump -d <database_name> -o <directory_backup>
And to "restore/import" that, i used (from directory_backup/dump/):
mongorestore -d <database_name> <directory_backup>
With this solution, you don't need to each all collections and export one by one. Just specify the database. I would recommend against using mongodump/mongorestore for big data storages. It is very slow and once you get past 10/20GB of data it can take hours to restore.