Deliver the Mythril
When you speak to Hilda, you can learn the [Dreadnought] Keyword. Show her the Mythril, and she will direct you to deliver it to Tobul in town. He can be found in the Weapon Shop. Once you give him the Mythril, a new counter will appear in the Armor and Weapon Shops which will sell mythril equipment. Similar Weapon Shops open in Paloom and Poft, where you will find the Mythril Axe and Mythril Bow.
Mythril gear is powerful and reasonably priced. The Armor pieces provide a boost to both Defense and Magic Defense without increasing Evasion or Magic Penalties. The Weapons are pricier but provide large Attack boosts. These pieces are the best you'll be able to buy for some time, so even if you can't afford full upgrades now, it's worth picking up more of them when you're in the area. Note that the only mythril item that's appropriate for mages is the Mythril Knife. The Silver Cuirass that you'll find in Bafsk is their armor equivalent, and surpasses the Mythril Armor at less than half its price as well.
Onward to Bafsk
Once you've handed over the Mythril to Tobul, return to Hilda and ask about the [Dreadnought] again. She mentions that a group in Bafsk is attempting to sabotage it. With that in mind, you have your next destination.
Bafsk is located on the coast beyond Poft, nestled in a mountain range. Cid will fly you there from Poft, but it's close enough that walking should be no big deal. The monsters in the Bafsk Area are similar to those you've seen before, and should present no serious threat.