you need to rebuild the files. Almost guaranteed the jpegs are not of good quality and not good to use as a working file.
I tell all my customers if they cannot offer the name of the font used, that I will get as close as possible. With the million fonts out there, it could take days to match the font.
You can also try posting the image here to see if others can ID the font or use
WhatTheFont : MyFonts