There are lots of options.
Easiest way would be to connect to a PC via USB and copy the files there. You'd probably be best off backing up the PC as well.
If your phone has an SD card, you could buy an SD card and copy the files there. If your phone doesn't have an SD card, you could copy the files to an SD card or USB dongle via a PC.
An alternative would be to rent some space in the cloud (Google sell it for $5/month) and back everything up to that - you'd probably want to do the actual file copies over WiFi.
