The duration of the migration process relies on various factors, such as the performance of the source store server, the number of entities to be migrated, and the Shopify API limit rate of your store plan. It is important to note that your source store will remain online and operational during the migration process.

You can estimate your migration time approximately from here https://migrationpro.io/migrations/shopify-migration/woocommerce-to-shopify-migration/#estimate-cost