[{"_id":ObjectId("630bd746956bba0f6f0ba448"),"a":[{"b":[[[{"c":"aaa"}]]]}],},{"_id":ObjectId("630bd746956bba0f6f0ba449"),"a":[{"b":[[[{"c":"aa"},]]]}],}]

db.collection.find({"a":{"$elemMatch":{"b":{"$elemMatch":{"$elemMatch":{"$elemMatch":{"c":"aaa"}}}}}}})