Hello @rmadhavan.
As far as what I understand, you have created a MongoDB service and a scripted service. And in your nodejs scripted service, you are trying to call the tables in MongoDB database.
In order to pull data from multiple tables, you can use DreamFactory’s data mesh feature. It allows you to combine data from two tables in the same database or you can combine multiple tables residing on different databases like MS SQL or MYSQL as well. You can find out more here - https://blog.dreamfactory.com/easier-data-marts-with-dreamfactory-data-mesh/
This is an easier way to combine two tables with point and click. You can have multiple tables joined together accessible through a single endpoint.
Scripting service
If you want to go to the scripting service route, this is a great place to start - https://guide.dreamfactory.com/docs/chapter06.html#modifying-existing-api-endpoint-logic. This will allow you to add the NodeJs scripted logic to your MongoDB service.
Let us know if you have any more questions