https://www.dropbox.com/sh/90bviwj4dhz8i83/AAATWKpkwXEVNQ8ai...Use this world: MCPE_V4_SH0WT1M3_ACHIEVEMENT_WERELD.mcworld
You can import the world onto an ios device by following this video:
Credit to OMGcraft - Minecraft Tips & Tutorials!
This chest will be in front of the lava. Simply drink a fire resistance potion, and then enter the lava.