there are only 200 chests you have to get them all including the treasure maps a few of the maps you get from the yellow sparkles
Turtle Map: Crystal Canyon East Side. Treasure location: West of Sapphire Town above the beach in the Turtle-like cave.
Dragon Map: Cannon Island all the way North. Treasure location: Crystal Canyon at the top of the crystal structure.
Cloud Map: Aboard the Ship Wreck west of Sapphire Town. Treasure location: Law’s Sky Island at the peak.
Pond Map: Aboard the Pirate Ship in Ruby Village. Treasure location: The lone rock in the lake in the Graveyard.
Stepping Stones Map: You get this for doing the Ghost in a barrel sidequest (Ruby Village). Treasure location: Sea Prison – Aquamarine next to the bridge.
Boulder Map: Law’s Sky Island North.
Ruins Map: For finishing the ‘Where’s Buggy?’ sidequest (You get it in Ruby Village after finding the Stepping Stones treasure). Treasure location: between 2nd and 3rd street Emerald Town.
source:
https://www.yekbot.com/one-piece-world-seeker-all-achievemen...