Scholarly or academic articles are different from practical or popular articles. Go through this tutorial to see how they differ.
You may have some projects like larger research papers where the professor asks for a specific number of scholarly articles. Usually this means no newspaper or magazine articles will count toward that number.
In the marketing classes requiring a research based paper instead of a marketing plan you will use databases like the ones listed below. Keep in mind some of these (like ProQuest and Busness Source Elite) happen to contain both popular articles and scholarly articles so you need to know what a scholarly article looks like. Sample scholarly article