Sierkowice
I believe the spelling is Sierakowice and it is about 50 km from Gdansk. There is also a village in the south of Poland by the same name, but if Joseph was from Prussia then Sierakowice near Gdansk may be the best place to start the search.
Church records are good place to search . The church in Sierakowice is Sw.Marcina. This church was rebuilt in the 19th century in place of the wooden one that stood before it.
The Parish addres is as follows:-
PARAFIA ŚW. MARCINA
ul. Kartuska 1
83-340 Sierakowice
tel. 058/ 684 79 25
e-mail: psierakowicem@pelplin.diecezja.org
Good luck