How you prune a raspberry depends on what type of canes you have, summer-bearing or fall-bearing (sometimes called primocane-bearing).
If the original canes produced fruit in the first year of growth then you probably have a fall-bearing type. In this case you can prune the fruited canes out to ground level or prune the fruited part of the cane out for a double crop the next year (see the link below for more details).
In you have a summer-bearing type then the canes in the first year of growth (primocanes) usually produce no fruit. In their second year of growth (floricanes) they will produce fruit on their branches. This cane dies after fruiting.
Here is an OSU pdf on growing raspberries. https://catalog.extension.oregonstate.edu/sites/catalog.extension.oregonstate.edu/files/project/pdf/...
Thanks for sending in an interesting question.