Here you can find some tips on how to write your internship plan.
Your plan should include a description of the company. What kind of product do they make or what kind of service do they offer? How many people are working there? Etcetera, etcetera.
What kind of period are you working for the company and how many hours? Also include the amount of study points you get for your internship and who is your supervisor from school. Write about the things you will learn from the internship or what personal skill you would like to develop.
Mostly you have to do some research for school. What is your assignment? And also what are your activities within the company? Sometimes you should make a table with your activities from week to week.