When reading database article results, look for the academic journal icon-see below
When reading the article's database record, select the journal's name which is hyperlinked. This will lead you to further information about the journal, usually indicating if it is peer-reviewed.
Note that an article can be from a peer-reviewed journal and not actually be peer reviewed. Editorials, news items, and book reviews do not necessarily go through the same review process, and are not what your professor wants when they specify research article. A peer-reviewed article should be longer than just a couple of pages and include a bibliography.