cylinder for 2D plain strain

Hi All,

I am very new to FEM process and ANSYS as well. 

I am trying to do a plane strain problem (2D) in ANSYS. 

My problem is  I dont know how to model primitives like sphere, cube, cylinder etc for 2D plane strain problem.

Like say can i model circle of 20mm radius for modeling sphere of 20mm radius???

Or can i model square of 50mm length for cube of 50mm.

May sound very dumb, but this is my geniune problem 

Thankyou for your time and help (in advance) 

Amit