Is there a bus from Orebic to Trpanj and from Orebic to Prapratno?
Yes, there are buses from Orebic to Trpanj – they run 3-4 times a day , depending of ferries arrival and departure to and from Ploce.
To reach Prapatno by bus, take any bus that goes to Dubrovnik and get off on crossroads to Prapatno.
Or can you go straight from Orebic to Ploce?
No straight connection is available. You would need to change buses at Doli (Jadranska Magistrala)
The easiest way to go to Ploce from Orebic is to take bus and then take ferry.