I was making a new mod and implementing its ore generation, but forge recently updated from .46 to .48 and I'm wondering if that's what's causing this error, but I don't know what else I could put in its place.

 

public class OreGeneration {

        public static void generateOres(final BiomeLoadingEvent event) {
        if(!(event.getCategory().equals(Biome.Category.NETHER) || event.getCategory().equals(Biome.Category.THEEND))) {
                    generateOre(event.getGeneration(), OreFeatureConfig.FillerBlockType.BASE_STONE_OVERWORLD, ModBlock.COPPER_ORE.get()
                            .getDefaultState(), 9, 30, 80, 30
                    );
        }
    }



    private static void generateOre(BiomeGenerationSettingsBuilder settings, RuleTest fillerType, BlockState state,
                                    int veinSize, int minHeight, int maxHeight, int perChunk) {
            settings.withFeature(GenerationStage.Decoration.UNDERGROUND_ORES,
                    Feature.ORE.withConfiguration(new OreFeatureConfig(fillerType, state, veinSize))
            .withPlacement(Placement.RANGE.configure(new TopSolidRangeConfig(minHeight, 0, maxHeight)))
            .square().func_242731_b(perChunk)
            );
    }


    }

This code works perfectly fine, and generates the ore into the world when I go back to the project

public class OreGeneration {

    public static void generateOres(final BiomeLoadingEvent event) {
        if(!(event.getCategory().equals(Biome.Category.NETHER) || event.getCategory().equals(Biome.Category.THEEND))) {
            generateOre(event.getGeneration(), OreFeatureConfig.FillerBlockType.BASE_STONE_OVERWORLD, ModBlocks.CHOCOLATE_ORE.get()
                    .getDefaultState(), 9, 30, 80, 30
            );
        }
    }



    private static void generateOre(BiomeGenerationSettingsBuilder settings, RuleTest fillerType, BlockState state,
                                    int veinSize, int minHeight, int maxHeight, int perChunk) {
        settings.withFeature(GenerationStage.Decoration.UNDERGROUND_ORES,
                Feature.ORE.withConfiguration(new OreFeatureConfig(fillerType, state, veinSize))
                        .withPlacement(Placement.RANGE.configure(new TopSolidRangeConfig(minHeight, 0, maxHeight)))
                        .square().func_242731_b(perChunk)
        );
    }


}

but this virtually the same code won't recognize .func_242731_b which is what I need to make it work because without it the game runs but it won't generate the ore. 

.48 is using official mappings, you need to find the proper name to use (I don't have .48 loaded, so I can't tell you what it is suppose to be).

I see it in older mappings on 1.16.4. The method is in net.minecraft.world.gen.IDecoratable. I loaded the new version and the method is called "count",