I use my xps 15 9560 laptop in combination with the dock wd15. It does work really well but I want to extend the dock usb type c-tm cable with about 6 feet. Does anyone knows what cable I can use? I need a extend cable with male and female connector.
You won't be able to. The reason the USB-C cable is shorter is because under current cable manufacturing technology, that's about the longest cable you can get that will carry USB 3.1 Gen 2 (10Gb) speeds and up to 130W of power, as required by your XPS 15. Just be happy you didn't get the TB16 dock in that case, since its cable is only 18" long because it has to carry Thunderbolt 3, which is up to 40Gb of bandwidth. Even if you find a USB-C extension cable, don't expect the dock to work properly if you add it. However, I haven't seen USB-C extension cables, possibly because USB-C is already confusing enough in terms of the variants of cables that are available. I wrote a long post about this all here if you're curious.