I can't find my built in microphone in my Mac mini

At the moment I'm trying to make some screen recordings with QuickTime Player, but it doesn't record any audio when I do so. So I searched up some tips and found some tips about how I had to choose the built-in microphone to add the sound of the screen recording. Now when I click on Input, it doesn't show anything. I'm also not 100% sure if my Mac mini even has a built in microphone.