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

Display settings

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.