Here are the general guidelines for writing a novella. I say general because, like all writing principles, they are subject to change. But ONLY if you have a good reason for the exception!
3. Use white space to designate scene changes
Instead of chapters, the novella usually employs white space between scenes. Some writers do break up a novella into sections designated by numbers. That’s a matter of style. Just don’t say “Chapter 1” etc. It's not necessary and interrupts what should be the flow.