Arrange the following groups in the proper
order according to their place in society: serfs, nobles, clergy, merchants,
monarchs, artisans, and knights.
(so basically they're asking what it'd look like in a pyramid )

What I would do is look in your history book or whatever and find out what each class ahs a part of. Your book or lessons should tell you the level of each or whatever. I would do that and If that still doesn't help. Look up each individual one and then make your conclusion. A good thing to remember is that a Noble is the highest class, A common clergy is the middle-class representative  (they aren't poor or super rich.) and a peasant is the lowest class. Then just break it down

Require the nobles and clergy to pay taxes.