I've seen something similar but not exactly like the question I have. I have a previous world that was generated normally and without ever having Biomes O Plenty installed. I am aware than now Biomes O' Plenty is a world generation type. Is it possible to generate new chunks that have Biomes' O Plenty biomes in a previously generated world? As far as I know I'm not able to change the world generation type of an already existing minecraft world without something like NBT edit.

EDIT:
I would try this but i'm not sure of the specific variable name for a Biomes' O Plenty biome type

• Biomes O' Plenty: 1.9.4-4.1.0.2049
• Minecraft: 1.10.2
• Forge: ???

I loaded up Biomes O' Plenty world gen in a separate world and the world gen variable was BIOMESOP, so i'm gonna try that and see if it works

It worked! Yay, thanks for the help guys