Hi,
http://mern.io/ might be a great introduction for you - Their docs are pretty good, and the starter kit is pretty sensibly laid out. When I was initially playing with MERN stack I read through the MERN.io starter and definitely came out the other side with a better understanding of proper structure and conventions.
I also found this hashnode post that seems to also be a nice introduction - hashnode.com/post/react-tutorial-using-mern-stack…
Good luck with your app!