Convert THUMBDATA to JPEG

As far as we know, there doesn't really exist a way how to convert or export out  JPEG picture from any of the THUMBDATA files, which is what thumbdata to jpeg conversion would be. These files are just cache files that contains thumbnail data for a picture that exist, or once existed in your Android phone. The main problem for recovery lies in the fact that .thumbdata file contains data from all pictures in one big data pile and there is no way how to recover just single picture.

Simply put, it is impossible to convert THUMBDATA to JPEG directly.
Thus, there is no so-called thumbdata to jpeg converter or a free online thumbdata to jpeg converter to be found.