[{_id:"xxxx","Type":"type1","Data":{"1":{"00":{"cont":"India"},"05":{"cont":"India"}},"32":{"41":{"cont":"India"},"44":{"cont":"India"}}}}]

db.collection.update({},[{"$addFields":{"arr":{/** first conversion*/"$objectToArray":"$Data"}}},{"$addFields":{"arr":{/** second conversion*/"$map":{"input":"$arr","as":"a","in":{k:"$$a.k",v:{"$objectToArray":"$$a.v"}}}}}},{"$addFields":{"arr":{"$map":{"input":"$arr","as":"a","in":{k:"$$a.k",v:{"$map":{"input":"$$a.v","as":"a2","in":{k:"$$a2.k",/** rename the field `country`*/v:{country:"$$a2.v.cont"}}}}}}}}},{"$addFields":{"arr":{"$map":{"input":"$arr","as":"a","in":{k:"$$a.k",v:{/** 1st backward conversion*/"$arrayToObject":"$$a.v"}}}}}},{"$project":{_id:1,Type:1,"Data":{/** 2nd backward conversion*/"$arrayToObject":"$arr"}}}])