/ How to find a burial site / records in Poland...
In the city of Debno (Dębno - but not Dembno today - old name) you can find two cemeteries. Both are the Municipal cemeteries, one by the Kosciuszki street, another by Wloscianska I street.
But the people you're looking for were most likely buried in the old cemetery in Debno (old. Neudamm/Nm. - Germany):
Now only a park there.
Info about the city: neumark.pl/main.php?miasto=debno&lang=en - check the comments of ancestors from this place.
...If this is the right place - in Poland there are several towns with the name of Dębno: en.wikipedia.org/wiki/Dębno_(disambiguation)