migrate existent content

I need to migrate all existing "Events" and "News Item" objects to folderish objects. How??

[pbauer]

See https://github.com/plone/plone.app.contenttypes#changing-the-base-class-for-existing-objects

I saw, but @@base_class_migrator_form does not show on (my) 5.2.3 Plone instance.
Also, "plone.app.contenttypes.migration.dxmigration.migrate_base_class_to_new_class" requires Products.contentmigration and Products.Archetypes.