Question

How many supporting details should you develop to back up your thesis?

Answer 1

I don't know that there's a specific number. What does your text say?

Answer 2

My research reports have often asked for three supporting details in each body paragraph. But I don't know if this helps.

Answer 3

OK, so if you have a thesis, and you have 3 supporting details (topic sentences) for that thesis, and then your whole paper will consist of 5 internal (body) paragraphs (plus introduction and conclusion), how many supporting details do you think each of those 5 topic sentences will need?

Think in terms of an outline:
https://owl.english.purdue.edu/owl/resource/544/01/

Let me know what you think.