why are u stuck?
well at the thundr plains uve gotta look at ur lil mini map and follow the red arrow
then from there u will fight a boss, who shouldnt be too hard

Boss Zalamander:
Zalamander is another tough cookie. He is a big dragon monster that hurls fire attacks at you along with a crushing paw swipe. His Flame breath attack nails all three girls for about 200 hp each which is easily healed afterwards. His other attacks are what you want to try and watch out for. The Tail Smash is good for a hefty 500 hp against each girl and his swipe can knock one girl down 750 in a single blow. The Zalamander is weak against ice attacks so be sure to nail him with some blizzards in warrior sphere mode. Keep the white mage healing and eventually you will receive a Crimson Ring from him and a Black Ring from the chest he was guarding.