"Favorites" Mail folder has disappeared.

I thank you for your reply, and though it didn't help solve my initial problem, it did at least let me know what the "Favorites" bar is (not labelled "Favorites" of course, as per new Apple lack of user friendliness.) I was looking for Favorites, because when I lost the folders on the left side of my Mail, another site had recommended trying the "Favorites."

At any rate, I did finally find my folders, there all along "On My Mac." I had tried that before, but kept clicking on the + sign, which is no help. Finally, I managed to accidentally maneuver around the + sign to get to the word 'SHOW," and voila, there were my folders. I've written this all down and saved it several places for next time, because no doubt I will accidentally click "HIDE" at some time in the future and be bamboozled all over again.