Please log into the web portal at https://zoom.us. Under "settings" >meeting (advanced)> you can turn on breakout rooms. When you complete that, next time you log into the zoom client installed on your computer, under your profile there is an option for "View advanced features". If you have invited your students to your zoom meeting, you will be able to pre-assign breakout rooms if you like, or assign them during your meeting.
https://blog.zoom.us/using-zoom-breakout-rooms/