This information from the service manual should help. The antennas are located behind the front bezel. Considering the type of antennas and length of the cables to the WiFi card, it would be rather difficult to relocate them but possibly you could place them on the back but that would do little to increase the range. But something like this might do the trick.
Firstly, where is the Bluetooth antenna on my Inspiron 3268? Secondly, is it possible to improve bluetooth range by extending/relocating the antenna? Or is there another way to extend the bluetooth range?
Bluetooth Antenna