The title says it all… I've tried several guides off Google .. There's no recovery on the iMac that had El Capitan… I have another iMac with High Sierra, so I how do I make a bootable El Capitan USB within High Sierra?

I have tried creating a bootable disk on transmac with no luck.

Every time I've tried to use the creatbootabledisk command on my High Sierra Mac, it throws an error and I have the files named the proper named according to which guide I'm following.