Both .pkg and .prt files come from P-CAD software, the first one is some kind of database and the other is CAD part. Thus it is extremely unlikely that some kind of direct pkg to prt conversion is possible, the fact that P-CAD has been discontinued years ago doesn't help either.
But more than one .pkg file type exists, so perhaps some other pkg to prt conversion is possible. Unfortunately, we have not found any specific information about such export.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.