Ok, checking their install SQL file and looks like the users table structure is as follows.
_jsn_users
Code:
`id`
`privacy`
`firstname`
`secondname`
`lastname`
`avatar`
`params`
`facebook_id`
`twitter_id`
`google_id`
`linkedin_id`
`instagram_id`
Fields configuration is stored in _jsn_fields and field valuess themselves I think might be stored in Joomla's _user_profiles table as it looks like they're just extending the core users class. Check the _user_profiles table and see if their profile data for those EasyProfile fields are there. Otherwise I don't have any idea where they're stored. You'll be able to migrate their _jsn_users data easy enough at least.