Cannot find connector for backlit keyboard - Inspiron 15 3558

Hello all!

Thanks in advance for the help, as I have done my research but I can't seem to solve my problem.

So, I purchased a Dell Inspiron 15 3000 Series (actual model is I3558-0954BLK). The model did not come with a backlit keyboard. Should have checked ahead :)

I found that apparently the 3558 model supports backlit keyboards, therefore I purchased a compatible keyboard that should fit models 3551 and 3558. 

When I followed the proper procedures to detach the original keyboard from my laptop, I could not find a slot for the "extra" connector that the backlit keyboard carries. After scratching my head for a while and doing some research online, I resolved to ask for your assistance. Here's a picture of what my laptop looks like without a keyboard. Could anyone be so kind as to point out where do I plug the other connector or help me understand why the laptop doesn't carry one? :)

Thanks!!!

Carmine

PS: In the picture, the green arrows I added show the standard keyboard connector & slot. The red arrow I added shows the extra backlit keyboard connector.