Open the following pages by setting page name as first argument of Ecwid.openPage function.
Open cart page in storefront: Ecwid.openPage('cart');
Pages list:
'cart''checkout/shipping''checkout/payment''checkout/place-order''checkout/order-confirmation''account''account/address-book''account/favorites''pages/about''pages/shipping-payment''pages/returns''pages/terms''pages/privacy-policy'