Sometimes you need to copy MariaDB data to MongoDB, you can use Withdata DBToMongo as MariaDB to MongoDB Copier (Converter / Transferor).
Works GREAT on Windows, Mac and Linux.
Support Windows, Linux, and macOS.
Support all MongoDB deployment types: standalone, replica set, sharded cluster, and MongoDB Atlas.
Can run in GUI mode, Step by Step, just a few mouse clicks.
Can run in CLI (Command Line Interface), for Scheduled Tasks and Streams, for Automation.
Start Withdata DBToMongo.
Login to MariaDB.

Login to MongoDB.

Click "Convert From Query" at task dialog.

then show the wizard.
1. Enter source MariaDB query.

2. Choose destination MongoDB collection and config fields.

3. Set rows options.

4. Export MariaDB query results to MongoDB collection.

Click "View", See MongoDB collection data.

Click "Convert From Table" at task dialog.

then show the wizard.
1. Choose source MariaDB table.

2. Choose destination MongoDB collection and config fields.

3. Set rows options.

4. Copy MariaDB table data to MongoDB collection.

Click "View", See MongoDB collection data.

Click "Convert Similar Tables" at task dialog.

then show the wizard.
1. Select source MariaDB tables.

2. Choose a destination MongoDB collection and config fields.

3. Set rows options.

4. Copy data from MariaDB to MongoDB.

Click "View", See MongoDB collection data.

Click "Convert All Tables" at task dialog.

then show the wizard.
1. Select source tables.

2. Target collections, choice "Import Type".

3. Map MariaDB tables to MongoDB collections.

4. Summary.

5. Batch copy MariaDB data to MongoDB.

Click "View", See MongoDB collection data.

After coping MariaDB data to MongoDB in GUI, and Saving "MariaDB to MongoDB" session, then you can:
How long does it take to copy MariaDB data to MongoDB?
Is it safe to copy MariaDB data to MongoDB using DBToMongo?
Can I batch copy data from MariaDB tables to MongoDB collections?