Your best bet is to go to the webcam manufacturer's website and down load the drivers.
However, if the webcam is not even appearing in Device Manager you could go to Dell's website and see if: 1) you can identify the camera, and 2) if Dell has drivers available for the camera. Use your laptop model to see if that leads you to the appropriate drivers.
Maybe a chat with a Dell support person or an email to technical suport will help identify the necessary driver and, more importantly, a download source.
Also be very wary of any websites claiming they can fix the problem - they are likely to pop up no matter what problem you are trying to resolve.