How to Hide Tweaker for Ninja Forms emails Premium monthly Admin Menus

function plt_hide_tweaker_for_nf_emails_menus() {
	//Hide the "Settings → Tweaker for Ninja Forms emails" menu.
	remove_submenu_page('options-general.php', 'admin-page-tweaker-for-nf-emails');
	//Hide the "Settings → Contact Us" menu.
	remove_submenu_page('options-general.php', 'admin-page-tweaker-for-nf-emails-contact');
	//Hide the "Settings → Upgrade" menu.
	remove_submenu_page('options-general.php', 'admin-page-tweaker-for-nf-emails-pricing');
}

add_action('admin_menu', 'plt_hide_tweaker_for_nf_emails_menus', 1000000000);

Where do I put this code?