I have a 1996 Chevy Blazer that is showing this code. According to my scan tool it is cylinder number 6 misfire. I have replaced that plug and wire. What else could be setting this code?

Back to the scan tool. P0300 is: “random misfire”. #6 cylinder misfire is coded P0306. You’re on the right track, but, the wrong cylinder.

How old are the other plugs. Likely just time to replace them all. As Hello wrote, that code is not specific to any one plug.