How to import contacts from Apple Contacts or vCard file
Open Apple Contacts app on your Mac, then select a group and then select contacts which you want to export. Then in the top menu bar, select File->Export->Export vCard and save these contacts as vCard file on your Mac.
Need to convert saved vCard file to CSV format
You can use this service to convert vCard to CSV:
https://tribulant.com/vcard-csv/
Upload there your exported vCard file, then select the next formats:
CSV
Coma
Then press convert and save CSV file on your Mac.
Use Import contacts feature in the app