Mongoexport is used to export a collection of a specific db in JSON or CSV format.
You can not export all collections using mongoexport in a single command, you need to make individual request for each collection.
But if you want to take a backup of mongo and want to restore it on another node, then, you must use mongodump command.
As stated in MongoDB documentation,
WARNING
Avoid using mongoimport and mongoexport for full instance production backups.
They do not reliably preserve all rich BSON data types, because JSON can only represent a subset of the types supported by BSON.
Use mongodump and mongorestore as described in MongoDB Backup Methods for this kind of functionality.
As already suggested, you can instead design a script, which will perform all the steps in order and will provide you with the desired results.
Thanks.