Both .let and .lbl files are used by CreataCard software for projects so if any program can somehow transform or export the data, it would be this software. However, we could not reliably verify whenever this let to lbl conversion is actually possible or useful.
Convert Creatacard letterhead project file to Creatacard label project file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert let to lbl on Windows
An old program for creating greetings cards
Convert from let file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.