How can I write an 8 to 10 page essay about Their Eyes Were Watching God with 5 to 6 sources using MLA format?

The first step you need to take in this assignment is to decide what sort of essay you are writing. There are several possible approaches to writing literary essays. In general, instructors include information about the type of essay they prefer in the assignment sheets for the essay or in the course syllabus. If you cannot find this information, you should contact your instructor, as if s/he expects a theoretical analysis and you do a close reading, for example, marks will be deducted from your paper.
Some of the basic approaches you could take for such a paper:


Historical: You could research some aspect of black people's lives in Eatonville, Florida, in the 1920s and look at the degree to which Hurston accurately represents historical circumstances. You might focus on one specific event such as the 1928 Okeechobee hurricane.

Cultural Criticism: Here, you might analyze how whiteness and blackness are portrayed in the novel, perhaps focusing on the moment when Janie becomes aware of her blackness. You could emphasize the way in which both races were defined by the "otherness" of the different race. 

Feminist: You could example the roles of women in the novel, especially in light of their relationships to money and power. You could discuss in what way Janie is a strong woman and consider the abuse she faces.

Linguistic: One important area of controversy concerning Hurston's work is her representation of African American dialect. You could write about whether her use of dialect is denigrating to black culture or whether it is empowering, asserting people's right to their own language.

Compare and Contrast: You could write a compare and contrast essay comparing Janie's husbands or comparing Janie with other women in the novel.

For finding sources, your university library website probably provides access to the MLA International Bibliography. If you enter the title of the novel as a search term, you will find several hundred scholarly books and articles on the topic. If you do not have access to the MLA bibliography, a good place to start research is Google Scholar. This is not the standard Google search engine but one restricted to scholarly sources that uses the Google interface. 
https://owl.purdue.edu/owl/purdue_owl.html