Can't find behaviour link between theme and social media

Hi all,

I have searched everywhere and I can’t seem to find where the theme tells the social media icon links how to behave. The social media icons are in the header. And all I’m attempting to do is open the facebook and twitter links in _blank windows. I’ve done this on other sites no problem, but I’m at a loss as to find the right spot to edit.
The site is: https://www.thebeadtrails.com/

This is the code in the header.php file:

<?php wp_nav_menu(
	array(
	'theme_location'	=> 'social_media_menu',
	'container'			=> 'div',
	'container_id'		=> 'social-media'
));
?>

Thank you in advance ??