Can't convert itunes playlist to mp3

I have tried multiple times and I have looked at multiple guides on how to convert a playlist from itunes into MP3. The only way that I found works the most is to go into Preferences then general then import settings and then to change it to MP3 encoder. After that, I highlighted the songs I wanted to convert then went into File, then Convert, and it shows 4 options. One of them is to convert to MP3. However, they are all grayed out. Does anybody have an alternative way to do this, or a way to make the MP3 converter not grayed out? I'm using Itunes 12.8.2.3 on a Mac Pro (Mid 2012)