Do a 'df -h' in the command line. It will show you what's mounted. If you have two cards and they are of different sizes you'll be able to identify which is which. If not, then do 'ls /media/mmc? (where ? is 1 or 2) and recognize your card by the content. Or, you can just rely on the common knowledge (see previous post) that the external card is /media/mmc1/ :-)