i am using gambit 2.3 (it is the latest version of gambit). i am unable to find the option of making meshes with polyhydril cells. please tell how i can make mashes with polyhydril cells

I think wou only can do that on the fluent 6.3 after a gambit mesh.

i guess the way to make polyhedral meshes from fluent is this:
[*] Create a mesh with tetras in gambit[*] use utility tpoly to make the polyhedral meshes

for tpoly you can use this command on console (for seeing how to use)

utility tpoly -h

it seems the command is

utility tpoly inputMesh outputMesh

Have you looked in the help file? I'm not sitting at my Fluent box, but my recollection was that it was under the grid tab. I don't believe it is not available for all mesh types.