I am an old MacIntosh computer user, but the oldest of my three computers is no longer on the internet because of incompatibility with modern (Verizon) routers; therefore, I now use my old (I think I bought it around 1996) computer only as a word pr

Welcome! Old Mac user here, too. We still have our first, a Mac SE/30 from about 1990.

It is difficult to recommend anything when we do not know at least the Mac model group to which yours belongs. There were many changes to the ports and expansion capabilities of all Macs through that period, and those affect what you can attach and how you attach it

One way to find the model/sub-model is to use a serial number lookup. Apple has such a function but it seldom if ever works on very old Apple products. If you wish to try, it is here:

Check Your Service and Support Coverage - Apple Support

As that may not work, the next best option is a third-party site that does the same thing but goes much farther back in time:

https://everymac.com/ultimate-mac-lookup/

Old Macs usually have a model name and/or number silkscreened on the front, like Performa 475; PowerMac 6100: Quadra 650; etc. Even that will help us immensely.

You can also take a snapshot of the front and back panels and post them here. In the toolbar at the bottom of a posting window, the second icon from the right will show "Image insertion" as you hover the cursor over it:

Click that and you will get a dialog box for navigating to the image files.

All that said, the last time I went on a search for a new printer that still supported OS9, I found nothing. Among the last companies to support OS9 in my searching was Brother, and they've not shown support for it for several years.

Even buying a used OS9 printer is dicey. There are so many different models of ink and toner cartridges today that old ones are dropped from manufacture much faster than before. You could find a compatible used printer yet be unable to get any cartridges--which appears to be your current situation.

Once we know what computer, we can also explore the "Doomsday" option of excising the hard drive and doing a direct connection to a more modern computer for file retrieval. With some this is easy---other, not so much.

Awaiting your follow-up information....

Allan