The "missing" letter is an "I", so the part number is KIA50N06, a MOSFET transistor.

Here is a marked up image showing how to reverse the polarity to your LED strips. The black lines are where to CUT the existing traces (seven places in total), and the coloured lines show where to add new wires, with little black ticks indicating solder points.

Note that you can actually do the soldering at any existing blobs within the same strips, rather than having to scrape away a lot of green stuff to do them exactly where shown.

Cheers