The third part of the Declaration of Independence is called the "List of Grievances," while the fourth part is called the "Resolution of Independence."
You can find this information by either referring to the original text of the Declaration of Independence or by searching reputable sources such as history websites or books. In this case, you can consult the websites I found during my search:
- http://www.ushistory.org/Declaration/
- http://en.wikipedia.org/wiki/United_States_Declaration_of_Independence
By visiting these sources, you can find a comprehensive breakdown of the Declaration of Independence, including its different parts and what was written in them.