lrdata - Adobe Lightroom Files
File Juicer will extract previews from Lightroom files. This can be a way to recover partially form a situation with missing photos where the originals have been deleted by accident.
lrprev - Lightroom Preview Files
Lightroom also save small jpg versions of the photos in lrprev files which File Juicer can extract. They are however rather small, so some AI enlargement work is likely needed
Drop the lrdata or lrprev file onto File Jucier and let it extract the images inside.
Apple Aperture Files
Users of Aperture and end in a similar situation where you need to extract pictures from approject files.