Advice:

Avoid using "I think" or "In my opinion."
Be clear from the beginning. Were the Mongols "barbarians" or contributors to flourishing trade networks and cultural diffusion? Make sure that you don’t change your mind halfway through.
It is okay to reference the other side (counter-argument), but don’t sit on the fence.
Make sure that your evidence supports your belief that the Mongols were barbarians or not. [Ex: Don’t say that they were barbarians because they killed many people but then talk about how they encouraged trade and cultural diffusion].
Before beginning your essay, compose a list of positives and negatives about the Mongols. Does the good outweigh the bad?

this is all of the stuff that is required