This pack is a data pack, so it lives inside a world's save folder rather than in your mods or resourcepacks folder. The pack's own instructions say to add it before starting your game, so the blacklist is active from the first time you load in.
Installing it into a world
1. Open your Minecraft game directory and go into the saves folder.
2. Open the folder for the world you want to protect. If you are making a new world, you can instead use the Data Packs button on the world creation screen and drop the pack file into the folder it opens.
3. Inside the world folder, open (or create) the datapacks folder.
4. Place the pack file in datapacks. Leave it as it came, and don't unzip it into loose files.
5. Launch the game and load the world.
Confirming it loaded
- With cheats or operator access, run the vanilla command
/datapack list. The pack should appear among the enabled packs. - If you added it while the world was already open, run
/reloador leave and rejoin the world so it gets picked up. - On a multiplayer server, the pack goes in the server's world
datapacksfolder, because data packs are handled by the world.
Once it is listed as enabled, any Drygmy farm in that world will refuse to generate drops from the blocked bosses, traders and spellcasters.