can we convert .gg files that is gridgen files to .msh ?

or can we import .gg files in gambit?

In Gridgen you need to export the blocks for the Fluent solver, which writes a .cas file. This can be opened by Fluent, and also imported into Gambit, I think.

ricky & Charles,

That's correct. Gridgen will export a .cas file for Fluent. Use the export commands in the Analysis Software menu (after selecting Fluent as your solver, of course).