Using a 2009 Mac Pro.

A while ago I put Linux on my ssd and accidentally wiped my Mojave partition.

I was enjoying Linux but need Mac OS for working at home now, and I can’t seem to install Windows on a separate hard drive.

I have another empty hard drive that I’ve formatted as FAT in Linux and when I do any of the keyboard shortcuts to go into recovery mode I get the question mark in the folder icon. If I do recovery mode key startup with the Linux ssd in it just goes to Linux.

I’m thinking the best way to do this is have the empty and drive in then boot into recovery mode but it just does the question folder thing.

Am I screwed at this point in getting Mac OS back on?

I did download Mojave a while ago and it’s on my external drive as a .app file but I haven’t found a way to convert it to .iso and make a bootable usb drive in Linux and use that.

I’m running Pop Os on my 2009 Mac Pro now.

Edit: I’ve been trying to format it with different options in Pop Os. It has type - hfs/hfs , APFS, boot etc then it has flags to select which are System Partition, Hide from the Firmware and Legacy BIOS Bootable. I’m trying a different combo of these options and no luck so far, still question folder icon.

I’m not sure if a combo of these options will make the computer recognize the hard drive and actually go in recovery mode.