Yo i might be a lil bit late but on 1.20.6 you can call BuiltInRegistries.ITEMS.getTagOrEmpty(*required tag*) to get an iterable of item holders, this might be possible on 1.18.2 as well. Then you get the items using for(Holder<Item> holder: iterable) or the .forEach(Consumer<Holder<Item>>) method, or convert the iterable to array/list/collection. When you get the holders, use the .get() method to get the items