I just double checked. (BTW: I am using SIERRA on an early 2011 MBPro.)
The path, for me, is exactly as I posted earlier:
~/Library/Application Support/AddressBook/Metadata.Note: There is NO long number between AddressBook/Metadata. See if anyone else chimes in about the long number series issue you mentioned. My guess is that the folders/files in your ~/Library/Application Support/AddressBook got inadvertently moved about so that the entire Metadata folder may have got moved (somehow) into one of the contact files (???).
You should be able to go to the current Metadata folder, whenever it is, and open it. All contacts (if any) would be listed there by default. The icons look like Rolodex Cards and WILL have a long number series associated with each contact.
Highlight one, for example, and then right-click GET INFO. Under the box marked "Locked" there is a little flippy-thingy called MORE INFO. Click on that and it will reveal the name/title and e-mail address of that Contact.
You could create a new folder called Metadata on your desktop. Open the "old" existing Metadata folder. Highlight and drag all the contacts into the new desktop Metadata folder you created. Send the "old" (empty) Metadata folder to the trash. Drag the "new" Metadata folder (with all the contacts) into folder ~/Library/Application Support/AddressBook.
Hope this is clearer and more helpful than my previous post.
