Extracting surface

Hello all,

I am working with a CFD solver based on the finite point method. My results are Ensight case files. I basically have two results files. One that contains the geometry (BE_model.case) and the other that contains the solution i.e the flow domain (model.case). I wish to extract a surface which is one of my outlets contained within the BE_model.case file , and plot the mass flow across it.
Could someone tell me how to do this?

Extract Selection ?