http://uwb25d43nnzerbozmtviwn7unn7ku226tpsjyhy5n4st5cf3d4mtflqd.onion/posts/tails/index.html
However, it can take weeks or years before that space is actually used for new files, at which point the old data actually disappears. In the meantime, if you look directly at what is written to the drive, you can find the contents of the files.