To access the 3D mesh settings and properties, you’ll need to open two panels: the 3D panel and the Properties panel (both found under the Window menu).
The 3D panel has all the components of the 3D scene, and when you click the name of any of those, you’ll be able to access its settings in the Properties panel. So make sure to always select the tab of the element you want to modify in the 3D panel before you change its settings in the Properties panel.