It can be found in 1 of 5 locations.
Bottom nearside corner of the windscreen.
If you lift the front boot lid & look to the left of where the battery is located theres a small plastic window on the bulkhead where you can see the chassis number.
Sticker on the rear of door frame (if its still there)
Then again lifting the front boot lid on the underside of it should be a build sticker listing vin no./paint code/list of codes for the options fitted to car. Link below (if it works) gives a list for said codes
http://www.986online.com/cgi-bin/ASI_Store.cgi?Search+XPage_optioncodes.html& finally the above info/sticker should be duplicated in your owners manual.
HTH