Where is the product key code located on my Dell Desktop? How many digits does it have?
Do you mean the desktop's product key? Or your windows product key?
The desktop key should be on a sticker somewhere on the case.
You can find your windows product key on the same sticker (sometimes. In the picture below, the blacked out text is the Windows product key, the first number beneath the word "Dell" is the model of the desktop).
If not, you can download, install and run Magic Jelly Bean Key Finder. This will list all the product keys of programs on your computer.