Migration of 3rd party extension

Hi Liz de keizer,
Thanks for contacting us. 
Our migration tool handles core Magento data migration only. Elements like CMS pages, extensions, customization … are separated tasks, and should be handled at your end.
It would be safe to contact with your theme and extension provider to check if those available for Magento 2.
Meanwhile, in case you missed, you can check out a few case studies below to learn more about our Pro version: 

-- We did use the Pro version ourself to help Winetasting.com – Migrate 382,047 customer entities to Magento 2
-- And this case study as well -- Freelaunch.nl used UB Data Migration Pro to migrate 230,000 products to Magento 2
-- Case Study: Successful Magento 2 Data Migration for Kwaaijongens.nl

 
Hope that helps.
 
Regards,
Ubertheme team