Follow the below path in your CIW.
File > Export > Stream
1. And in the run directory field, specify the desination where you want the GDS to
be.
2. Specify the Library Name, Top Cell Name and the View Name of the layout.
3. Fill up the Output File as *.gds, where * is your cell name.
4. In Options, select the Case Sensitivity preserve.
5. Now give OK