The Recording panel, where you can disable What You Hear (what SoundBlaster calls Stereo Mix) is in
Control Panel/Hardware and Sound and finally the Sound Panel, Recording section.
If you are using Windows 10, RIGHT click on the start button (lower left) and you can access the Control Panel.
I haven't found a way to post screenshots directly on this forum. What you would need to do is post the screenshot on some host server and then provide a link to the screenshot.