Database
[{"GENUS_DATA":{"File_6489248.ZLM":{"MeterID_6489248":{}}}},{"GENUS_DATA":{"File_12345.ZLM":{"MeterID_12345":{}}}}]
Query
db.collection.update({},[{$set:{GENUS_DATA:{$objectToArray:"$GENUS_DATA"}}},{$project:{GENUS_DATA:{"File-Name":{$first:"$GENUS_DATA.k"},"data":{$first:"$GENUS_DATA.v"},}}}],{multi:true})