There is no direct connection from Parga to Kefalonia. However, you can take the bus to Preveza, take the bus to Pátra, take the bus and ferry to Argostoli, then take the bus to Kefallinia Airport. Alternatively, you can take the drive to Nydri, take the car ferry to Fiskardo, then take the drive to Kefalonia.
How to get from Parga to Kefalonia
From Parga bus to Preveza, bus to Pátra, bus and ferry to Argostoli, then bus to Kefallinia Airport. 9 h 27 min 42€. From Parga drive to Nydri, car ferry to Fiskardo, then drive to Kefalonia. 4 h 22 min 61€.