Looking for the birth record of michael mcmann born in December 1858 in Norfolk Co. Canada. Were do I find these records since Canada did not keep birth records before 1869?

It was not required for births, marriages and deaths to be registered prior to 1869 - it does not mean they weren't kept. Vital registrations were not the primary source of a birth record - they were copies of birth records sent to the government. Usually it was a parish record (church record) that first recorded a birth, marriage or death. If you can't find a vital statistics registration, try church records.