MongoDB Connections' and use different queries

HI Team,

In order to use aggregation in ready api, please give us sample code, I am facing issues, how to apply different aggregation.

HOW to put Unwind data into query

below is sample code, 

$unwind:
/**
* path: Path to the array field.
* includeArrayIndex: Optional name for index.
* preserveNullAndEmptyArrays: Optional
* toggle to unwind null and empty values.
*/
{
path: "$Folder.List.items",
includeArrayIndex: "legIndex",
preserveNullAndEmptyArrays: true,
},
},