A plane
a cylinder a cylinder
a cone!, It has a top and a bottom
Such a figure is a triangle-based prism.
A nonagon is a 2-dimensional figure and so has only one face.
a prism
A triangular prism
A prism.
A cylinder
A triangular prism has 2 triangular faces and 3 rectangular faces.
That would be a triangular prism - assuming you mean a 3-d figure. You usually don't refer to a 2-D figure as having "faces".
a cylinder
A triangular based pyramid has only 4 faces.