Obviously a mid-90’s, what bike is it?
I would guess that is an old 90’s Suntour fork not a newer one. Maybe 63mm, but no more than 80mm. You can probably use an 80mm.
While thru axles are better, mountain bikers have probably ridden millions(?) of miles with QR and discs. Just make sure they are tight and use steel internal can QR’s.
There are cheap new 80mm forks on eBay for less than $100 if you want cheap and feel you need suspension. If you don’t need suspension you can go rigid. You also have to weigh the cost of the disc system.
If your old Suntour fork works well, don’t get rid of it. I don’t know who made it. I wasn’t aware Suntour made (labeled) forks back then.
And it doesn’t matter what you paid for the bike, if it is pretty much unused, in this market it would probably fetch more than $100. Between the pandemic buying and a nostalgia for 26ers, I don’t see a lot of good cheap ones out there. But I’m not flipping either.
John