Hi, @MikeZheng-3371 Welcome to Microsoft Q&A, Thanks for posting your query.
What are the number of collections and avg size of collections?
I would recommend if the collection sizes are small - in double-digit Gbs, better to simply use mongodump/mongorestore else go with ADF or Spark.
you can find this document for more information.
Please let me know if the information is helpful.
Regards
Geetha