I have a CD / DVD drive as in the title. I have the KX07 firmware loaded on it. I am looking for a newer KX11 firmware for it. I need this newer firmware because my drive cannot read some CDs. I did a google search but only found the older KD11 firmware on Dell's website and the KX11 is nowhere to be found. There was this firmware on the manufacturer's website, but the website was closed and the zip file with the firmware was not saved on archive.org

So, this is a stock Dell optical drive? I did some looking and found the same thing you did. Personally I would not trust a firmware download from anywhere but the manufacturer. I don't know if you have a laptop or a desktop, but replacing an optical drive in a desktop is quite easy. Another option would be to purchase an exterior optical drive. I have one for my desktop and it works great.

This is Sony Optiarc drive, it is USB CD / DVD drive. Of course, I have a desktop computer, so if there is no software for this drive, I can replace the drive

They have a "contact us" for support for the Optiarc drives. Have you tried that route?

https://www.optiarcinc.com/