Finished?
I know 0 about USB drives. Am assuming this 32GB will hold all my pictures and files (no videos). When do I know the files are all transferred?
It is hard to say if 32GB device can hold all your files. With modern digital cameras (and especially raw DSLR pictures) picture sizes can be pretty big. Also scanned documents can be pretty big.
Probably it would be safe to say that on average, 32GB device can hold about 8000 pictures (assuming about 4MB per picture).
The best way is to check the actual size your pictures and files (on Windows you can right click the folder and check the properties).
As for how to know when all files are copied, assuming you are using Windows, then you should see a progress bar indicating the copy progress.
Note that you should make sure to safely remove the device to prevent loss of information.