The leading practice is to use NetSuite as your master record of data so that your data is updated in NetSuite and syncs to the marketplace/cart via FarApp. This setup alleviates the need to update data in multiple marketplaces/carts. Instead, it can be updated on one platform - NetSuite - and synced to multiple marketplaces/carts at once.
However, there are certain connectors where product data can be synced to NetSuite from your marketplace/cart (even though this is against leading practice). To see if this is supported by your connector, please visit the the FarApp products page (https://www.farapp.com/products/).
If you are in the process of initially setting up NetSuite and would like to migrate your product data from the marketplace/cart to NetSuite, the recommended approach is to export your data from the marketplace/cart via a CSV file and then import that file into NetSuite. This NetSuite help article gives an overview of the CSV import process - https://tstdrv1261834.app.netsuite.com/app/help/helpcenter.nl?fid=chapter_N342646.html. There are also companies that will help you migrate your data from your marketplace/cart. Once the product data is in NetSuite, FarApp can then be set up to automatically sync it to the marketplace/cart whenever it is updated in NetSuite.