How to Hide Stackable - Gutenberg Blocks Admin Menus

function plt_hide_stackable_ultimate_gutenberg_blocks_menus() {
	//Hide "Stackable".
	remove_menu_page('stackable');
	//Hide "Stackable → Getting Started".
	remove_submenu_page('stackable', 'stackable');
	//Hide "Stackable → Settings".
	remove_submenu_page('stackable', 'stackable-settings');
	//Hide "Stackable → Documentation".
	remove_submenu_page('stackable', 'stackable-documentation');
	//Hide "Stackable → Go Premium".
	remove_submenu_page('stackable', 'stackable-go-premium');
	//Hide "Stackable → Useful Plugins".
	remove_submenu_page('stackable', 'stackable-useful-plugins');
}

add_action('admin_menu', 'plt_hide_stackable_ultimate_gutenberg_blocks_menus', 11);

Where do I put this code?