Are you the original owner? If so, it's up inside the right-hand side wheel well behind the headlight, assuming nobody moved it. If you bought it used, it's most likely been moved for easier access. Some people relocate it behind the tow hook cover, some relocate it to somewhere they can reach it from underneath, or the radiator intake openings.
It's stainless steel and looks like a bike brake cable.
Download this catalog:
https://www.porsche.com/all/media/pdf/originalparts/usa/986_USA_KATALOG.pdf
Go to page 218 and it's item number 12
Or you can search this part number in the catalog: 996 511 521 00
One thing you can try is loosen up the bumper cover from underneath and look up in there. Unfortunately, I don't recall if you can remove the bumper cover completely without the frunk open.