From Bulbapedia, the community-driven Pokémon encyclopedia.
Each location in the Generation VIII games has its own identification number used internally by the game. They are enumerated here, in order. Locations with alternate names have their alternate names listed as an index number after the main location. Locations lacking an alternate name have the following index number blank.
Index numbers between 00248 and 30000, 30020 and 40000, 40087 and 60000, and above 60004 are filled with null data. If a Pokémon references an index number for met location that does not exist in that game, it will be displayed in that game as "in a faraway place".