Well if the phone can still turn on, then you can get files off of it. However, if the phone won't turn on, well then you are out of luck on getting anything off of it.
All you need to do is turn it on (if it is working) then use the phones file manager app to move files from the device to the card. Note, you can't move apps, just files. That may take a while though. Or you can connect the phone to a computer via USB cord and move all the files over to an empty folder on the computer.