The Cavagna regulator most likely has 1/4" NPT female threads on the ports. The hoses you need would have 1/4" NPT Male threaded ends. The other major choice is the inverted flare which I do not believe will fit your Cavagna regulator. The only other info you need is the length, think about what you have and if you are happy with that length then just duplicate it or go to the next longer size. Best not to go shorter to avoid connection issues.
Don't forget to buy some yellow teflon tape for the threaded connections.