I was intrigued by your question as I have thousands and thousands of pictures (128GB) on my computer. I am unsure of what you are calling "cards" of pictures. I did a google search for a "usb for photo storage with sorting" . Several types of USB photo keepers/photo sticks showed up. Did a quick look at them on Amazon and the reviews are not very good. Mainly because they copy your photos but they are not organized or sorted in any way plus they seem to be expensive.
This is what I do, I bought an 1TB external hard drive and just copy my files including photos to it. They remain sorted as I have them on my computer (by date and subject in folders) and I can easily retrieve them should my computer die.
Hope this is helpful....