OpenTerrainGenerator.zip\OpenTerrainGenerator\worlds\Biome Bundle\WorldBiomes
in the
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ReplacedBlocks: (STONE,minecraft:concrete:8),(GRASS,minecraft:concrete_powder:13),(COBBLESTONE,minecraft:concrete:7),(SAND,minecraft:concrete_powder:4),(SAND,minecraft:concrete_powder:1),(GRAVEL,minecraft:concrete_powder:7),(STATIONARY_LAVA,STAINED_GLASS:1),(DIRT,minecraft:concrete_powder:12),(STATIONARY_WATER,STAINED_GLASS:3),(NETHERRACK,minecraft:concrete:15),(SOUL_SAND,minecraft:concrete_powder)
i used notpad++ to get in to it