db={from:[{foo:[{bar:[{_id:ObjectId("63f508eedd2962118c37ea36")}]}]}],collection:[{_id:ObjectId("63f508eedd2962118c37ea36"),field1:"helloworld"}]}

db.from.aggregate([{"$unwind":"$foo"},{$lookup:{from:"collection",localField:"foo.bar._id",foreignField:"_id",as:"foo.bar"}},{$group:{_id:"$_id",foo:{$push:"$foo"}}}])