Export contacts on Yahoo account

Sign into Yahoo mail
Click on the "Contacts" button, and then go to Actions -> Export.
Select the "Yahoo CSV" option
click the "Export Now" button
select somewhere on your computer where to save this file, and click "OK".
How to move your contacts from Yahoo to Gmail

https://www.youtube.com/watch?v=of1qJLN6g_k

Source:Youtube

Import the CSV file into your Google account
Sign into Gmail.
Click Gmail at the top left corner of your Gmail page, then choose Contacts.
Click the More button above the contacts list and select "Import..."
Click the Choose File button.
Select the CSV file you generated from Yahoo, and click the Import button.