You shouldn't need anything else to view the card. That is, if your tablet has a SD card slot, then all you need to do is insert the card. It should be able to view whatever is on it.
That is as long as the card wasn't encoded or encrypted. If it was, then only the device it was encoded on/in can view it, and for encryption, you would have to decrypt it.
Now if it wasn't altered (as mentioned above) but your tablet can't view it, then you may need a SD card reader and connect it to a computer to view what is on the card.
Lastly, if the tablet isn't working, but the SD card has info you want, you can try connecting the tablet via USB cord to a computer and it should allow you to view what is on the card. Otherwise a card reader would...