What is the treatment if there are 2 kidney syones of size 6.6mm and 26mm for a 24yrs male

You have to see your doctor... they have a variety of options. There isn't a single treatment that's always used.

Chemical treatment (medication) ultrasonic to break up the stones, or merely let them pass. If they are not causing any pain or issue, they may do nothing.

26 mm is an extremely big stone. Sure it is 26mm and not 2.6mm?

Good catch. I assumed 2.6. 26 I am sure, they would be rushed to surgery.