The Z Order Tools let you change the layer of the selection relative to other objects in the layout.
The Layers Tab will show the vertical order of the layers, and you can move layers up and down through that interface as well by clicking and dragging a layer up or down.
Sometimes layers can be hidden or unseen in the layout if Show Colors is turned on and these layers are underneath other layers or on the bottom. Inlines or strokes are commonly hidden from view. In wireframe mode, you will see the vector outlines of all layers, so it is a good idea to toggle the colors off to make sure you see all data.