My son took a plea deal of 10 years for trafficking methamphedamine and promoting contraband he has a confidential informant can we find out who it is even though he didn't take it to trial

Confidential means private or personal. There is no provision that allows for the naming of a confidential informant (CI) after a case is over. If he took the case to trial, the law would allow the accused to face the accuser. He waived that right when he took the plea. Sometimes there is no CI, the prosecution is good at bluffing defendants into taking a deal saying there is a CI when none exists.