Hi,
Here is a link to the service manual for your laptop.
This will assist you in replacing the antenna cables.
http://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_inspiron_laptop/inspiron-15r-n5110_service%20manual_en-us.pdf
Here is a link to just one supplier of replacement cables for your laptop.
http://www.pchub.com/uph/laptop/421-92052-21927/Dell-Inspiron-15R-N5110-Wireless-Antenna-Cable.html