DOCS-7898: mongoexport fix example

Author: kay-kim

source/reference/program/mongoexport.txt

@@ -279,7 +279,8 @@ Specify the:
 
 .. code-block:: sh
 
-   mongoexport --host mongodb1.example.net --port 27017 --username someUser --authenticationDatabase admin 
+   mongoexport --host mongodb1.example.net --port 27017 --username someUser --authenticationDatabase admin --collection contacts --db marketing --out mdb1-examplenet.json
+
 
 Alternatively, you use the :option:`--uri <mongoexport --uri>` option to specify the host, port, username, authentication database, and db.