Before all these DSLRs came along there was this stuff called film...

Slide film is the opposite of the negatives you would be used to getting when you have a roll of film - it is the positive of an image, a lot of commercial jobs still need it today for it's amazing quality. I still have some in a fridge somewhere...should really use it up at some stage!

Either get yourself a scanner that will scan negatives and slides (may list it as the "positive" in the settings) or if you want a good quality version take it to a lab like Fitzgeralds or Churchills. I had a cheap Epson scanner years ago that did it, was about $300 when I bought it. If you're not printing it big that will do the job fine.