I see. So it may well be the card or data. If you still have the old phone, I would put the card back in it and then connect the phone to a computer via USB cord and see if you can move the files off the card to an empty folder on the computer. If you can't put it in the old phone, or don't have it any longer, you can try doing the same through the new phone. However, it could have issues reading it through the new phone.
Once you get the data off the SD card, then I would suggest formatting the card and trying again to put files on it and see if the new phone can read it. Just make sure you leave the data on the computer and only copy it back that way there is no risk of loss. Should it work, great. If not, then you just get a new...