My information is sketchy, but maybe this will help. Niepla had two parishes, one in Szebnie and the other in Warzye.I have visited the Szebnie cemetery but found that it had been badly damaged in the war. Graves were three deep. I received no information from either parish.
You might wish to contact the civil office in Jaslo. The email address is gmina@gminajaslo.pl. I did receive a reply from them. I was also instructed to contact the archdiocese in Przymyl. I hope you have better luck than I.