need level 3 spells

You should be able to find some level 3 magic in Ur. Here is a map of the overworld. Not sure if you'd be able to go all the way back from your current location. If you have a Fira Rod or a Blizzara Ice Rod, you should be able to use those to cast Level 3 magic.

Also in that temple, you are always stuck on mini, so my best advice is have them all be spell casters. I would also have 2 white mages so you can heal your party more efficiently, and two black mages to attack. Also make sure they're in the back row so they havea slightly higher defense.