X Squishling X

Hello everyone! Recently, I have been attempting to create advancments for my Minecraft mod. I have a custom biome that I have created, and am trying to create an advancment that unlocks upon the player entering this custom biome. I have managed to get the advancments working for vanilla biomes, but when trying to enter my own biome in I don't know what to enter for the biome id. I have tried using F3 in-game to get the ID, but this just gives me the name ('Snowy Plains') which doesn't work in the biome ID, with or without my mod id before it. I have also tried using a forge method that returns a biome id in number form, and this also failed to give me any working results. I'm wondering what the correct way to provide a biome ID for a custom advancment featuring a location requirement is, and if anyone knows the answer, your help would be greatly appreciated!