Sometimes your professor will assign a certain number of sources.
Other times your professor will state "enough to be comprehensive or thorough."
The more sources you find, the more selective you can be. You want to cover the range of research and thinking on your topic.
Use GET IT @UST Libraries to get the full-text if not available in Google Scholar.
You want your reader to understand the breadth and depth of your topic.
Read through all of the materials you have found. Then, choose a broad range of perspectives and types of sources.
Choose the strongest article(s) from each perspective.