How do I get my desktop Icons back on my primary display?

I fixed this in in Display settings (System Settings --> Display). The three monitors I use are different sizes, but after dragging the monitors so that they were aligned along the bottom axis, my icons returned my primary monitor on the left

Like this

I am running Gnome and have a dual monitor setup. If I hit Alt+Space a menu pops up on my primary display and "Move to Monitor Right" or "Move to Monitor Left" is highlighted. Click that selection and the icons move to the other screen.