I want to let customer to select any 3 products listed in my custom page and when click on add to cart the 3 product will be combined into a single product called Package A.
The total price should be combine of 3 product, and Package A description should be the product selected.
This will not be possible if you are using Wix Stores. You can however custom build this kind of store using Corvid & Wix Editor elements.
You can give a custom package name & store the items as an array along with the visitor’s user ID in a custom ‘cart’ database. You can display items based on the user ID & allow checkout using the same.
However, developing a custom coded store is no small task and unfortunately you will not find any tutorial which will show you how to build a custom store from scratch but you can find many tutorials which show you how to do things like Creating a checkout flow using the Wix Pay API .