To get Cart feature first you have to install HikaShop package downloaded from project website: hikashop.com, even free version will be okey for this purpose. Then publish HikaShop Cart Module in "top-right" module position, remember to add "ecom-top-cart" in module Class Suffix field. Check also following module settings.

Also default Joomla search module should be published in this same module position, but it doesn't request any additional suffix.