[{_id:ObjectId("635286ea1c66064140400d67"),"retailerRequestId":82,"receive":[{"receivedQty":100,"receivedDate":"2015-12-01 18:16:46","receivedStatus":{"statusId":435,"status":"RReceivedFull"},"tagItems":[{"tagSerialNumber":"137438955172","status":"RReceivedFull"},{"tagSerialNumber":"137438955171","status":"RReceivedFull"},{"tagSerialNumber":"137438955170","status":"RReceivedFull"},{"tagSerialNumber":"137438955169","status":"RReceivedFull"},{"tagSerialNumber":"137438955168","status":"RReceivedFull"}]}]}]

db.collection.update({"receive.tagItems.tagSerialNumber":{$type:"string"}},[{$set:{receive:{$map:{input:"$receive",in:{$mergeObjects:["$$this",{tagItems:{$map:{input:"$$this.tagItems",in:{$mergeObjects:["$$this",{tagSerialNumber:{$toLong:"$$this.tagSerialNumber"}}]}}}}]}}}}}])