Tried to convert an old mac time machine into an external drive--did I bork it?

My dad was getting rid of his time machine and asked if I wanted to try to use it as a regular external drive. I said sure. I use Windows, so I was planning to reformat it. I googled how to do it, and the general gist was to get onto the disk manager on a MacOS machine and reformat the drive to exFAT then use it on a windows PC.

Well joy of joys, we hopped onto my dad's mac and formatted the drive just fine (did an erase and picked exFAT from the dropdown), but now we can't detect this drive at all. On any machine. His Mac can't see it, his PC can't see it, and neither of my PCs can see it either. All the instructions we looked up were about adding a letter for an internal drive when a computer can't detect it, but this is an external drive so that didn't seem applicable.

Has anyone encountered this before? Any idea what we missed?

EDIT: I'm pretty sure we borked it. After removing the drive from the time machine and manually setting it up in my computer I STILL could not get it to display in disk management or BIOS or otherwise get the computer to acknowledge that it exists so I can initialize/format/use the thing. I think I have to accept that we borked it when we reformatted it.