The best way to search for peer-reviewed journal articles is to use a literature database. Databases index the research articles in journals and have powerful search filtering tools. Most databases also have quality standards that journals need to meet to be included, which limits your chances of encountering predatory publications. Databases typically do not house the journal articles themselves, but will link to where you can find the full text.
Preprints are early versions of research articles which have not yet been peer-reviewed. Scientists may choose to disseminate their research as preprints before submitting to an academic journal, which can make the research reported very cutting edge, but these reports should be read critically as they have not yet been reviewed by other experts.