Contact Merging

This is 15 years of collected contacts and I’ve no doubt there are duplicates due to technical issues over the years. How would I best consolidate the contacts, remove exact duplicates, and merge duplicates containing different contact info and NOTES into one contact. For example, say I have two vcards on Ben Smith and one has …just the full name and cell number and the other has the full name, plus an email address and NOTES….. You’d need to identify those duplicate names and then merge the combined info into one contact.