You can save contacts in a VCF from Address Book Card data files (*.abcdp) using the default Contacts address book manager in Mac OS X. Probably done with some sort of export function.
Convert Address Book card data to vCard contacts.
We have found one software suitable in our database for this conversion.
Apple macOS / Mac OS X software - convert abcdp to vcf on OS X
The Mac OS X Address Book is a little handy application with loads of features that are often overlooked by most users. Its very useful for for organizing your contacts, but Address Book's real power is that it works with many other applications. Its an integral part of Mac OS X operation system. From Mac OS X Mountain Lion the Address Book will be renamed to Contacts.
Convert from abcdp file
to vcf file
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.