You want to migrate "MRP areas" to S/4 HANA Cloud.
You can use the mass processing apps we have (scope item 1RM as a guide) to extend the MRP area information. You cannot use this app to create the root object though, i.e the material.
So use the migration cockpit to create the material first as much as possible and then extend it using the tool mentioned above to add the MRP area information. You can do this via file upload, very similar to data migration cockpit.
Please see the video explaining how to do it: https://youtu.be/J04BjwxeRuQ
SAP Knowledge Base Article: 2715529 - Migrating MRP Areas in S/4HANA Cloud