On the 1861 census they are living in Moorsley, which is in the Houghton registration district.
Between 1861 and 1871 there is only one Sarah Ord death in that district, unfortunately just before ages were put on the indexes!
Sarah Ord
June Q 1864
Houghton 10a 200
If you order the certificate from Durham registrars
www.durham.gov.uk (online services)
unfortunately that years deaths are not searchable online, but the name and quarter should do it for the form, if you specify things to make sure it's the right one it shouldn't cost you anything, unlike the GRO who charge about £3 if it's the wrong one.