Oh, one of those. I didn't think it would be anything quite that ancient. There are two types of font suitcases. Type 1 PostScript suitcases that only hold the screen fonts of a set, and legacy Mac TrueType suitcase fonts from OS 9 and earlier.
It was at least a few versions of macOS ago that stopped allowing Type 1 suitcase screen fonts from appearing if the matching outline printer fonts were missing, so this has to be a Mac TrueType suitcase. Though I still have to be guessing a bit without having a copy of the font to fully check it out.
If my guess is correct, then the good news is it's already TrueType. Bad news is it's an old 8 bit set. Which in itself isn't terrible, but it also isn't a Unicode font. I also don't think it will be very many more years before the OS doesn't allow their use anymore. If you wonder why I would say that, you're in High Sierra, and the font appears normal on the desktop. In Big Sur, such fonts now all appear with a generic Unix EXEC icon. They still work, but that's a pretty big hint from Apple this font type is on its last legs.
There are multiple online font converters that can handle this. You simply upload the font and choose what font type you want it converted to. Definitely choose TrueType OpenType. Here's one:
https://convertio.co/font-converter/
Or, do a search for "online font converter" and try a few.
