how can I update my power mac g5 from 10.4.11 to 10.5?????????

I have a power mac g5. Its a powerpc processor running 10.4.11 at the moment. Before it crashed and I had it repaired it was running 10.5.8. How can i get back to that version. 10.4 is just simply not working for the applications and etc that I use. I can not even use itunes for goodness sake. Someone please help!!!!!!!

P.S.

I currently have no disc. Lost in the process of moving from Miami 😟