Edit for "Become a Vendor Page" in Dokan multivendor plugin on wordpress

Question

I need to find the file path to add a predefined country code to the phone number field I looked for "become a vendor.php" file in the dashboard I managed to change from the registration form, but if a user is already a customer and he wants to join in as a vendor he needs to click "Become a vendor" and somehow this is different from Dokan Regsitration form Regards,