In order for you to determine what information can be used for a paper on Harriet Tubman, you are going to have to make sure you narrow down your focus in your research paper. Specifically, what about Tubman are you going to be analyzing in the paper? This is going to be critical in selecting suitable information for your paper. I think that finding information is secondary to the development of this focus, called the thesis statement. For example, are you going to focus on her success as a conductor on the Underground Railroad? Are you going to study her role in bringing about the Civil War? Are you going to be focusing on her background prior to being a conductor? This focus will not only give direction to the paper, but will also help determine what can constitute as suitable information that can be used for the paper.
In terms of broad information, I have included some links to study guides that can be found on enotes. These are solid supplements on books about Harriet Tubman. These can be a starting point for you. They give solid background on Tubman and can be used as helpful in constructing the broad strokes and background on Tubman. Yet, the development of your thesis statement, or focus to the research paper, is going to be the most important element in determining what you need, what research will be helpful, and how your paper will take form. Regardless of what research you use, without this thesis statement, challenges in writing your paper will emerge. Conversely, if you are able to establish some level of focus on what you want your paper to discuss, finding research suitable to your topic and constructing the paper becomes a bit easier.