The safest backup is on to a disk that's stored in a fireproof box but you could settle for backing them up to a PC or laptop.
Connect the device to a computer and look for the folder DCIM then Camera. Select all the files and copy them across to a new folder you create and name.
A less safe backup is within the device itself. Go to the Play Store and search for Nandroid. Back up to an external SD Card but if the phone goes missing or is stolen, the backup goes withh it.