|Presumably it (wifi) isn't simply disabled or switched off?|
Does the device (wifi adapter) show in the system hardware profile (device manager)?
describes how to check that area.
Is it there and is there a yellow exclamation mark next to the wifi adapter (under the network adapters "button")?
Meanwhile... going to the Dell.com site support area and entering your service tag details one finds this list of drivers available for Windows 8.1:
Have you checked there that you have all drivers as listed?
And another Dell (ftp) site where there are most/all current drivers listed...
You "may" find the the Windows 8.0 driver will work OK?
Failing which contact Dell and see what they suggest?