Thanks for the help.
Here's the updated query for 2.2
INSERT INTO xenforo.`xf_reaction_content` (content_type, content_id, reaction_user_id, reaction_date, content_user_id)
SELECT 'post', dbt.contentid, dbt.userid, dbt.dateline, post.userid
FROM vBulletin.`dbtech_thanks_entry` AS...