Database

[{"_id":ObjectId("60468a01010e8f08b0f794d6"),"conversationMetricName":[{"metric":"nConnected","stats":{"count":3}},{"metric":"tAbandon","stats":{"max":319012,"min":7372,"count":1,"sum":326384}},{"metric":"tAcd","stats":{"max":319012,"min":7372,"count":1,"sum":326384}}],"conversationInterval":"2021-02-17T18:30:00.000Z/2021-02-18T18:30:00.000Z","__v":0},{"_id":ObjectId("603faf38150786680421b52b"),"conversationMetricName":[{"metric":"nConnected","stats":{"count":19}},{"metric":"tAbandon","stats":{"max":319012,"min":7372,"count":2,"sum":326384}}],"conversationInterval":"2021-02-18T18:30:00.000Z/2021-02-19T18:30:00.000Z","__v":0}]

Query

db.collection.aggregate([{"$project":{"_id":1,"__v":1,"conversationInterval":1,"metrics":{"$arrayToObject":{"$map":{"input":"$conversationMetricName","as":"el","in":{"k":"$$el.metric","v":"$$el.stats.count"}}}}}},{"$replaceRoot":{"newRoot":{"$mergeObjects":["$metrics","$$ROOT"]}}},{"$project":{"metrics":0}}])

Result