There are a growing number of graves to mark in cemeteries across Ocean County this Memorial Day, as those who served in World War II, Korea and Vietnam continue to age. The job of making sure all 18,264 of those graves is marked with an American flag falls to John P. Dorrity, the director of the county’s Veterans Service Bureau, and the volunteer members of veterans’ and civic organizations such as the Scouts. “We had a 9 percent increase in the number of graves from last year,’’ he explained. Ocean has more veterans, 68,000 living within its borders, than any other New Jersey county. Many …