Migrate to Volto#
Please read the chapter Migrating from Plone Classic UI to Volto of the Plone Upgrade Guide. This explains mostly why you need to do what and how to use the form @@migrate_to_volto by hand.
You can (and should) use the power of that feature in your exportimport-based migration as described in collective/collective.exportimport
The package contentimport has a version of @@import_all called @@import_to_volto that contains all the code used for that.
This will transform the imported content to work with Volto:
Change html to blocks
Turn Collections into Documents with Listing Blocks
Turn Folders into (folderish) Documents
Integrate default-pages into these Documents
A rather new alternative to that solution is to use collective.transmute to convert the data exported with collective.exportimport before it is imported so that the migration to Volto is already done by importing the converted data with plone.exportimport](plone/plone.exportimport).
Instead of using plone/blocks-conversion-tool to transform html to volto blocks it uses the new package collective.html2blocks for that task.