It depends on how the objects were compiled. Assume a program named PGMA. Try STRDBG PGMA to see if a listing view is presented. (We can assume that a source view won’t be presented. And the library might need to be specified too.) If one shows up, then it’s fairly easy, though potentially tedious, to retrieve the source from the listing view.
The question asks about “cle”, which would normally mean “ILE C”, and about “rpg”, which would normally mean “OPM RPG” which might be RPG II, RPG III or RPG/400. Variations might be necessary if any of those are not what was meant.