Many of your professors expect you to produce your papers in MLA format. Produced by the Modern Language Association, this format and style guide is now in its 9th edition. The newest version is very similar to MLA 8, with most of the changes being around use of inclusive language and expanded guidance for citations, formatting, and especially avoiding plagiarism.
Please remember that keeping up with writing and style guides is generally the work of academics and librarians. Many professors are creatures of habit, and most are very busy, so your professor may not have noticed this shift to MLA 9 or simply may not like the new system. With that in mind, you should consider checking in with your professor to make sure they want you to use MLA 9 as opposed to an older (now defunct) MLA.
This list from Purdue University's Online Writing Lab (the Owl) shows the biggest changes for the 9th edition: