Database
[{_id:"5f3d4e5e01e06f0007335233",name:"Walmart",createdAt:ISODate("2020-08-22T17:42:09.908+00:00")}]
Query
db.collection.aggregate([{$group:{_id:{year:{$year:"$createdAt"},month:{$month:"$createdAt"}},numShops:{$sum:1}}},{$project:{_id:0,numShops:1,date:{$concat:[{$arrayElemAt:[["","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"],"$_id.month"]},"-",{$toString:"$_id.year"}]}}}])