Looking for field family burial cemetry

I am not sure where my great grandparents are buried or indeed born but my grandfather lived in letterkenny , my father was born in letterkenny in 1910' 

grand father was in the donegal militia as a bandsman! Would he have been stationed in lifford or letterkenny ive drawn a blank 

Can anyone. Point me in the right direction, they would of belonged to the church of ireland