If AchievementBadges is not available
AchievementBadges can be a beta feature per wikis. Go to your preferences → Beta features → Check AchievementBadges and save it.
Achievements Special page
The AchievementBadges extension creates new special pages that can be used to find achieved and not achieved achievements.
Where can I see my badges?
Badges are an upcoming feature and not developed yet.