Hi Bimal,
Thank you for posting your query in Microsoft Community.
I do understand as I checked it myself, DELL Inspiron N5110 WIFI driver is available on the manufacturer's support website. However, it is not available for Windows 8.1. The driver which is available is for Windows 8.
I would suggest you to download both Windows 7 and 8 drivers from the support website and try installing driver in compatibility mode for previous version of Windows and check.
First try to install driver for Windows 8 in compatibility mode. If that does not work, try installing Windows 7 driver in compatibility mode.
Download these drivers: Dell - Product Support
a. Right click the driver installation file and select Properties then tap or click the Compatibility tab.
b. Place a check in the Run this program in compatibility mode for: box.
c. Tap or click the drop down box and select a previous operating system, then tap or click OK.
d. Try installing the driver and check.
You may refer to: **Make older programs compatible with this version of Windows** (information holds good for Windows 10 as well)
Hope this information is helpful. Please feel free to reply in case you face any other issues with Windows in future.