Missing Mono option

Hello, I just acquired Audacity 2.3.2 on Windows yesterday. I wish to erase vocals on a downloaded MP3 song. I followed video instructions on YouTube but my first problem is highlighting the right track after splitting stereo tracks. When I hit the select button on the bottom track it highlights or greys out the upper or left track. Then after selecting invert on the drop down menu for Effects it goes through the inversion process but there is no mono option after that. Basically, I’m just missing the mono option. I need help. Please! Thank you.

See my reply here: https://forum.audacityteam.org/t/where-is-the-mono-option/53004/2