Dear srikanth,
Area and perimeter of drain/source have a great dependency upon your utilized process/technology and the way you are going to lay it out (e.g. to the number of fingers). However in most simulators you can find the default values of these specifications for your device by using the following parameters, "as" (source area), "ad" (drain area), "ps" (source perimeter) and "pd" (drain perimeter). However as I said after laying out your devices, these values should be changed (if required) to mirror some impacts of layout in your schematic simulations.
Regards,
EZT