Why Minecraft just crashed when starting this mod?

So I first converted MCCreator's homemade mods from 1.12.2 to version 1.14.4 so that I can use these mods on 1.14.4, but unfortunately the Minecraft simply ended after starting and received this crash report:

Does anyone have any idea why this is the case and how to fix it? Because Googlen brings me nothing, because everything is only in English. That's why I need your help.

Hello your problem is surely because you have converted the modification mod because there's no IF query in the main class, so that is not possible

Did you extend the landing gear too early?

And where can I find the main class?

Let's say it so you have to have the program Eclipse but basically you can only use the mods in 1.12.2. : /

What does chassis mean?

You must have the Eclipse program

Where did you get that from?