Welcome to Roanoke Linux Users Group Monday, March 19 2018 @ 12:52 AM EDT
About a year ago, I did a fresh install of Ubuntu 12.04 on an older Dell laptop. One of the few issues was with the WiFi connectivity.
There is a proprietary driver for the Dell Wireless 1395 WLAN mini-card (which is actually a Broadcom BCM 4312 under the hood) provided by the manufacturer here.
Also, more information about detecting and installing alternate drivers provided in the Ubuntu documentation is worth reading: Identifying Your Broadcom BCM43xx Chipset (PCI)
The steps that I discovered was: