I canot access my files because the screen with

Hello,
The screen login window opens to allow login if you activated the security feature. With the security enabled you cannot even open the drive under Linux or Mac OS.
You may try to download the LaunchPad from SanDisk and reinstall it. But I am doubtful, because any security feature worth its bytes should disallow it. I suppose you can always try to reformat the drive, but you files will be lost.
Hope it helps.