This article explains how to turn on the new meeting experience within Teams. This will allow many new features including pop out meeting windows and large scale view of up to 49 participants.
Step 1: Click on your initials/ icon on the top right-hand corner.
Step 2: Click "Settings".
Step 3: Tick the box next to "Turn on new meeting experience (New meetings and calls will open in separate windows. Requires restarting Teams.)"
Step 4: You have enabled the new Teams meeting experience.