What book part would you use to see how the book is organzied and where each part begins?

You would check the Table of Contents. You would see if the book is organized into Units and if the Units are subdivided into Chapters. You would check to see if each Unit has a name that refers to a time or a specific topic. Then you would see if the Chapters (or other subdivisions) further divide that large topic into smaller parts of the topic. To find out where each part begins, you would see which pages are listed. You might check to see if each Unit is the same length as other Units. You might check to see if there are quizzes or tests associated with the units and chapters.

There might also be a part of the book called "To the Student." This part of the book might explain in better detail how the book is organized and why the author chose to organize it that way.