You definitely need to have more than one. It depends on the stress distribution (thick), but normally a rule of thumb could be about 4 linear elements, or 2 quadratic elements are a start.
See this on how to set that:
https://forum.ansys.com/forums/topic/element-mid-side-nodes-ansys-19/
Shell elements you need a surface body - if the body is thin and you do not care about any through thickness phenomena say at the location of the rolers and you want just to capture bending, then use shells.
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