We now have an importer available for FusionBB3. With this importer you can import your users, categories, forums, topics, posts, pollsl, private messages, file attachments and galleries into UBB.threads.
You can follow the basic import instructions
to get you started. There is a readme file in the zip that contains special notes for this importer.
* We are unable to import Link Forums at this time.
* We are unable to import subcategories. Any forums belonging to a subcategory will be assigned to the main category instead.