Users searching for db to jpg this conversion are usually just searching for a way to export and save pictures out of some thumbnail database found in Microsoft Windows, including for example thumbs.db file
It is possible to browse through and view the contents of these files using programs, such as Thumbs.db Viewer or even some common graphics editors and viewers. Unfortunately, conversion back to original images seems unlikely as these databases are generated for caching purposes to speed up the loading of images in your system and only contain resized version of the original.
At best, you could recover 96x96 sized thumbnails of the original files, but there is no way to recover the originals, hence you probably won't find any kind of thumb.db to jpg converter.
Open DB file Open JPG file