If you can buy Font Awesome Pro and use legally, you can use it by the code under this sentence.
function change_font_awesome() {
// Deregister Font Awesome Free.
wp_deregister_style( 'font-awesome' );
wp_deregister_script( 'font-awesome-js' );
//Enqueue Font Awesome Pro CSS (example).
wp_enqueue_style( 'font-awesome-pro', get_stylesheet_directory_uri() . '/library/font-awesome-pro/all.min.css', array(), '5.9.0' );
}
add_action( 'wp_enqueue_scripts', 'change_font_awesome' );