Going by what you wrote I am assuming you mean that you have a card in the phone that is already made to be "Internal" storage, and want to move the files (photos) to a different SD card? If that is the case it really depends on if you are just putting them on the card as storage, or to transfer to a different device (where the card normally is used). Also, another factor will be if you want to move them all at once (not really possible using the phones file manager) or move them one at a time.
The fastest way to move the files would be to connect the phone to a computer via USB cord. Copy the files you want to put on the card to an empty folder on the computer (or just move them if you don't want to keep copies on the phone). Once...