I think this is it:
Code:
UPDATE vb4forum.user as old LEFT JOIN vb3forum.user as new ON (old.userid = new.userid + 1)
SET new.post_thanks_thanked_times = old.post_thanks_thanked_times
This sets the vb3forum database from the vb4forum database. I think what I posted above assumed that you were going from vb3 to vb4 (at least as far as the table prefixes were concerned). Speaking of which, if you have table prefixes you need to add them.