To transfer a website from one engine to another is not five minutes. Just making a backup is not enough. The second point Shopify has its own subtleties. Therefore it is better to contact the company for example https://www.makebecool.com/services/migrate-to-shopify . Online stores have a lot of products. It takes a long time to do it yourself and still when transferring a site from one engine to another, technical issues will arise. For example, how to install ssl?