I need help getting a test biome/dimension to work in 1.21.10

Hello! I'm very new to creating data packs and I'm trying to get a grasp on more complex topics like worldgen.
I want to test out a custom biome just to see if I can even get it to work. Right now I have a folder structure that looks like this inside my "testbiome" datapack
data > testbiome > dimension > test_dimension.json
data > testbiome > worldgen > biome > test_biome.json
in the test_dimension.json file I have the code:
{
  "type": "minecraft:overworld",
  "generator": {
    "type": "minecraft:noise",
    "settings": "minecraft:overworld",
    "biome_source": {
      "type": "minecraft:fixed",
      "biome": "testbiome:test_biome"
    }
  }
}
In the test_biome.json file I have the code:
{
  "has_precipitation": false,
  "temperature": 0.8,
  "downfall": 0.4,
  "effects": {
    "sky_color": 7907327,
    "fog_color": 12638463,
    "water_color": 4159204,
    "water_fog_color": 329011,
    "grass_color": 65280
  },
  "carvers": {
    "air": [],
    "liquid": []
  },
  "features": [],
  "creature_spawn_probability": 0.0,
  "spawners": {},
  "spawn_costs": {}
}
I thought this alone would be enough for me to create a custom dimension with different colored grass. However when I run the command 
"/execute in testbiome:test_dimension run tp @s ~ ~ ~"
I get the error unknown dimension 'testbiome:test_dimension', even though I know the datapack is loaded and working (I loaded a test function and it is working). 
So, if anyone with 1.21.10 worldgen experience could help me discover what I put incorrectly within the json files, or what I'm missing, I would really appreciate it. Thanks!