Duplicate data from Mongo Atlas to on-premise mongodb

I need to duplicate records about 400 million records from Atlas Mongodb to self-managed Mongodb without any changes. After finishing migrating data, these 2 databases also need to be synchronous.

I tried to use MongoSourceConnect with Kafka, but it took too much time to duplicate the data. I would try to export data from Atlas and import to the database, then we setup the MongSourceConnect with Kafka. However I am afraid that I would lost some data during migration process.

I like to know if we can specific starting time or resume token to start change stream in the mongo source connector?

Where does the mongo source connector save the resume token, and how to view it?

How to convert the oplog to resume token?