Mongoexport / mongodum with --uri

During my studying of MongoDB I tried to dump a collection from training course’s mongo database. I tried both mongodump and mongoexport . My shell command is like
mongoexport --uri="mongodb://,," --collection=collection-name --out=collection-name.json --ssl

When I run the command, nothing happened: no response, no new local files, no errors, only cursor flashes.

How can I export collections by the uri ?

Try uri string

mongoexport --uri="mongodb+srv://" --collection=xyz --out=xyz.json 

modify above to suit your cluster