"Remove duplicate contacts" not working on a Mac

I just completed migration of the data from my old Mac to a new one running Monterrey, before which I backed up everything to the Time Machine. On the new Mac I found several duplicated contacts in the address book. I followed the steps Contacts-card>Look for Duplicates>Merge & repeated once, after which, no more duplicates were found, even though I could still see many contacts in duplicate. I found one set of contacts under iCloud & the second under On My Mac. But no matter how many time repeating the search, the system could not detect the duplicates. I am thinking I should consolidate all contacts in iCloud, by selecting & dragging all On My Mac contacts into iCloud, then run a search/merge for duplicates, & that will hopefully eliminate all On My Mac duplicates. Does this make sense? I just want to make sure I don't set off a nuclear event with my contacts.