Drop in your server folder and the app will handle the rest: find your world/,
world_nether/, and world_the_end/ folders, then merge the Nether and End
into DIM-1 and DIM1 inside a single world folder — no manual file shuffling required.
Upload the whole server folder, or just the one folder that has the three folders mentioned above inside it.
CraftBukkit-based servers (Paper, Spigot, Purpur) register each dimension as its own World object, so the Nether and End get separate top-level folders — world_nether/, world_the_end/ — instead of living inside world/. Both Vanilla and Fabric only look for dimension data at DIM-1/DIM1 nested inside the primary world folder — anything outside that path is never read. This tool copies the region/, entities/, and poi/ data from your Nether and End folders into world/DIM-1/ and world/DIM1/, and zips up a single world folder laid out the way Vanilla and Fabric expect
saves/ for singleplayer. For a server, it must be named exactly world (or whatever level-name is set to in server.properties).