Terrain control how do i use ReplacedBlocks:

OpenTerrainGenerator.zip\OpenTerrainGenerator\worlds\Biome Bundle\WorldBiomes
in the
#######################################################################
# +-----------------------------------------------------------------+ #
# | Blocks | #
# +-----------------------------------------------------------------+ #
#######################################################################
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

World edit /replacenear radius stone concrete
Or /replace stone concrete

Second one you can use when you've already defined an area with the wand and it replaces blocks only in the area. The first material is the one to be replaced and the second one is what it's replaced with. You can also list multiple things separated by a comma and no space

/replacenear 100 stone gravel,cobblestone
That will replace all stone with gravel and cobblestone 50% each randomised placements

ReplaceBlocks is obviously a command provided by a plugin, so without knowing the plugin it's kind of impossible to comment on it.

But you don't need it, the vanilla /fill command can also do the trick. For example like so:

/fill -305 55 269 -299 55 276 minecraft:concrete 8 replace minecraft:stone

So you basically determine the area using 2 specific locations, then you specify what block you want to use to fill (light gray concrete) and finally you specify which blocks it should replace. Doing that will make sure that only the stone blocks get replaced.