Used or not?
If you can see a narrower strip of film coming out of the cassette, your 135 film roll is still unused. If you can’t see any leader strip, photos have already been taken with the roll and there are images on the film – don’t try to open the cassette because exposing the film to light would destroy them. You should take it to a photo lab to have the pictures developed. Have a look here to see if you have one nearby.