Hi All Preparing my 2009 iMac for sale I erased the HD and tried to reinstall high Sierra in recovery mode. I have no idea how but something went wrong. When I start the Mac I get a folder with a question mark. I know this means it can find the boot sector. I’ve tried all of the restart methods. None work. I think i need a USB boot drive. However my current Mac is Mohave and I can’t download high Sierra Any suggestions?