It’s really on a case by case basis. There’s really no generalizing that can be done. It’s seriously all individual. The course number itself doesn’t matter so much as the course content. I really don’t think it would make a difference trying to specifically do 2000s levels courses. It all depends on what your plan of study dictates. Make sure to double check everything with your adviser.
Other mod response:
Honestly, I think it just depends on the class… I’ve taken some pretty hard 2000 level classes and some easy 3000 level classes— what you probably want to pay attention to more is the second number, which tells you how specific the topic/material is, because a 3800 class is gonna need more background than a 3100 class. But again that’s just sort of a general guideline and may or may not be accurate everywhere.
I would say you should try to talk to your advisor about what’s typical for people in your major, or ask friends if you can, because each major is very different. However, if you’ve never even taken a 2000 level class and you’re concerned, maybe wait until next semester. If there’s a class you absolutely would LOVE to take that’s a 3000 level and you’re a strong student, I wouldn’t let that stop you, though.