ok, if you have some stems with fruit on now, do they look like new stems - green and fresh - or do they look brown and a bit drier?
green fresh looking stems with fruit on now - autumn raspberries
brown, drier-looking stems with fruit on now - summer raspberries
autumn raspberries bear fruit on new young stems each year, so you cut all of the stems on each plant (there will be multiple canes in a clump for each plant) right down to the ground in the spring, they then re-sprout and bear fruit on those new stems next autumn
summer raspberries bear fruit on older stems, so you cut back ONLY the stems that have fruited this year, again right to the ground, but leave any new-looking stems as they are, as they will carry the fruit next summer
if you can't decide once you've had a look don't worry, as you can just cut them all to the ground in the spring and then see what happens - if you have autumn ones they will produce fruit on the new stems next year, and if you have summer ones they won't produce fruit on the new stems next year, but they will the year after.
Hope that's all useful and not too confusing!