Hi jamilmashrke,
Based on the screenshot that you have posted, Chipset drivers are not installed and the Wireless card appears to be listed as a PCI Ethernet Adapter with exclamation mark.
May I know the exact system model? Also, you have mentioned installing Ubuntu, so do you still have the Windows installation? If yes, which version of Windows is installed in the computer?
You may visit the following website: http://dell.to/10GaKAc
Enter the computer's service tag and click “Submit”. In the next page, click Drivers & Downloads tab, and then select the operating system installed. Drivers compatible with your computer will be listed on the page.
Download and install all drivers listed under the category “Chipset”. Then, under the category “Network”, install the listed Wireless card’s drivers. Also, download and install “Dell Quickset” if it is listed under the category “Application”.
Awaiting your response!