I chose Harriet Beecher Stowe to compare and contrast with julius caesar, but can only think of how they both helped improve the lives of slaves.
Well, that is all you need! Start writing. I know the situation you are in. You feel overwhelmed because of some factor... maybe a lack of sources or how long the paper is supposed to be. But all you need to do right now is write a 1-page paper about how caesar created a change for the slaves. 1.) background, 2.) how he made a change, 3.) discuss before and after.
After you do that, repeat the process for Stowe. You can write 3 paragraphs about each, and you will have 2 full pages. Add an intro at the start and a conclusion at the end, and you have 4 pages.
How long does the paper need to be?
Even if it needs to be 20 pages, start with this small task: one paragraph about the BACKGROUND of the caesar situation.
The journey of a thousand miles begins with a paragraph topic sentence -- Confucius
;-)