Errors from the start

From the start, I gotta create a workspace (aka name of mod). I called it Darkmod. Then when I add a mob, it just gives me this log. According to the log, there's also something wrong with the workspace(?)

C:\Pylo\MCreator183\forge\build\sources\main\java\mod\mcreator\darkmod.java:31: error: cannot find symbol
import net.minecraft.block.Block;
                          ^
  symbol:   class Block
  location: package net.minecraft.block
C:\Pylo\MCreator183\forge\build\sources\main\java\mod\mcreator\darkmod.java:48: error: cannot find symbol
    public final List<Supplier<Block>> blocks = new ArrayList<>();
                               ^
  symbol:   class Block
  location: class darkmod
C:\Pylo\MCreator183\forge\build\sources\main\java\mod\mcreator\darkmod.java:74: error: cannot find symbol
    public void registerBlocks(RegistryEvent.Register<Block> event) {
                                                      ^
  symbol:   class Block
  location: class darkmod
C:\Pylo\MCreator183\forge\build\sources\main\java\mod\mcreator\mcreator_reaper.java:28: error: cannot find symbol
import net.minecraft.client.model.ModelBiped;
                                 ^
  symbol:   class ModelBiped
  location: package net.minecraft.client.model
4 errors

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 5s

How do I fix this? I tried creating a second workspace and switching, as I read somewhere, but that doesn't help.