Need information on my grandfather, gunners mate 42-757

My grandfather, Milton C Hayden from Louisiana was in WWII as a gunners mate. He enlisted under age so he may have used his fathers name, Raymond A Hayden.

In his class photo the sign says 42-757.

He was possibly stationed in Australia.

I tried to call the USNaval office and was transferred to several other offices and no one was able to help.

Any info or advice on how to learn more would be greatly appreciated!