You can't really convert .pet files to .2fs, even though both files originate in Pupply Linux. First is a installation package, the second is used to save a current version of the system "a snapshot". No way to convert one to another.
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.