You cannot write to a memory card that is located in the Canon A620.
The camera firmware will not permit it.

There have been some reports of some Sony Viaos not reading larger capacity memory cards.

You will need to buy a card reader and attach it to your computer via a USB port.
Then you can write photo files to the SD memory card.
Since the card has been used in a camera, it is best to delete all files and folders (via the computer) from the card first.