There are several ways in which Drupal facilitates a site migration from a different platform or system. Both the Migrate and Feeds modules are exceptionally useful in this endeavor.
Should part of your migration include an eCommerce migration, you may want to consider the Commerce Feeds module.
This module enables you to import commerce product entities into your site. Because of the way that Commerce separates the product entity from the node entity, you will want to either consider multiple imports (one for product entity, one for node entity) or implement hook_feeds_after_import() to create nodes for each product created.
As part of your import process, you may also want to consider using the Feeds Tamper module to help prepare your imported data for the expected structure by product entities. This is exceedingly useful when importing multiple reference fields (term or entity). More on that in a subsequent post.