Plug your USB OTG cable into your phone, connect a USB device to the other end (a USB stick for example). Go to /sdcard/usbdisk with a file manager on your phone & the USB stick will be mounted as r/o & the files on the stick will appear in this folder.
If it's important enough to cause you grief if it's lost, back it up. No excuses
Trolling for thanks is lame
Does Samsung's auto-brightness implementation crap drive you to self-harm ? A solution !
Failure to search is the leading cause of male impotence on XDA
If you don't know how to recover if things go wrong, what are you doing flashing custom roms ?