Apple's 6 pages of exhaustively meticulous step-by-step instructions: How to move your iTunes library to a new computer - https://support.apple.com/HT204318 Use this if you suspect any of your media are not in the standard location (iTunes Media folder).
My one-sentence summary if you always use iTunes' default preferences settings: Copy the entire iTunes folder (and in doing so all its sub-folders and files) intact to another drive, hold down the option/alt key (shift on Windows) while starting iTunes, and when requested to select a library select the iTunes Library.itl file in the copied folder (Open a different iTunes Library file or create a new one - https://support.apple.com/HT201596).
Most other things such as Home Sharing probably won't work on a computer that old.
If your iTunes purchases are the same vintage as the computer you may have a lot of DRM protected files and will need to authorize the other computer too.
Edit: It is nice for those helping here (we are all volunteers) not to do duplicate posts. I see somebody else already answered this elsewhere.
syncing music from PowerPC G4 to Apple or Windows device