How to make a MongoDB query sort on strings with -number postfix?

You can use

db.collectionName.find().sort({title: 1}).collation({locale: "en_US", numericOrdering: true})

numericOrdering flag is boolean and is Optional. Flag that determines whether to compare numeric strings as numbers or as strings. If true, compare as numbers; i.e. "10" is greater than "2". If false, compare as strings; i.e. "10" is less than "2". Default is false.

MongoDB can't sort by numbers stored as strings. You either have to store the number as an integer in its own field, pad with leading zeroes, or sort the results after they've been returned from the database.