You need to get a ferry tank installed and increase your range to at least 1200NM. I ferried a Piper Seneca I from Copenhagen to Johannesburg around 5 years ago. We exited Europe from Malaga in Spain and flew to Agadir in Morocco. From there we flew to Bamako but I would suggest Dakar in Senegal. From Dakar route to Accra in Ghana and then cut across the ocean to Libreville. From Libreville we flew nonstop to Maun in Botswana, but that was an 11 hour flight which you would be challenged to make in a PA30. We had 2 hours fuel remaining when we landed in Maun but we also had 800 litres of fuel in our ferry tanks plus full wings when we left Libreville. You'll have to find somewhere between Libreville and Maun to stop for Avgas. There may be some in Luanda as I've seen Beechcraft Barons and Cessnas there. I believe Angolan Air Services, if they are still around, have a few piston engine aircraft in their hangar.
You'll obviously be flying a reverse routing but that should give you a good idea of a route.
Good luck.