It should be on your software restore disc. Open 'Install Applications & Classic Support'. Some versions of this have an option of what to install. If this is the case, choose Classic and then install it. Otherwise, in Finder go to the Go menu, select 'Go to Folder...' and type '/[name of software restore disc]/.images/'. Hopefully this will display a folder full of disk images. Find the OS 9 one, probably called 'OS9General.dmg'. Mount that and copy the files to the root level of your hard disk, and Mac OS 9 is installed. 🙂