You should create an import mapping and map the json elements on your own objects, then you can add them to a datagrid.
https://docs.mendix.com/howto/integration/consume-a-rest-service
Arjun,
In your microflow, you need two additional retrieve actions. After the REST call, add a retrieve that gets Items from Root via Association. Next at a retrieve to get JSONObjects from Items via Association. The second retrieve will give you a list of JSONObjects that you can manipulate, store in a persistable entity, etc.
Note that your retrieves should always be via association when working with Non Persistent Entities.
Hope that helps,
Mike