How to Export Yahoo Mail Contacts

Step 1: Open Yahoo Mail, Click the Contacts icon at the top of the right side panel.

Step 2: Place a checkmark in front of the contacts you want to export or place a checkmark in the box at the top of the list
to select all contacts.

Step 3: Select Actions at the top of the contact list and select Export from the menu that appears.

Credit : https://www.lifewire.com/how-to-import-addresses-from-hotmail-yahoo-others-into-gmail-1172008