Hi there i been trying to locate a birth index so i am able to purchase a birth certificate of my 3rd great grandfather.

i just received his marriage certificate this morning, he married in 1863 and was aged 24 which makes him born approx 1839 / 1840

and all of his census say he was born in DULBIN IRELAND
but i am unable to locate his birth, aswel as a death

his wife was called Mary dogget,
and his father was called John Quinn, i am unable to find out his mother name as i am unable to locate any census before 1871 for peter,

can someone please help me, any help would be very much appreciated