It seems that Apple QuickDraw is the only program that can reliably produce .3df files and as such is the obvious choice for pic to 3df conversion. There exist many different graphics formats that use pic extension, so not all may always work.
Convert Picture image to Quickdraw 3D file.
We found one software available in the database for this conversion.
Apple macOS / Mac OS X software - convert pic to 3df on OS X
A 2D graphic library used on Mac
Convert from pic 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.