You will need to use product slug or ID to import reviews for your WooCommerce products
1. Get WooCommerce product's slug
Login to your WordPress admin > Products > All products.
2. Hover on a product that you want to get slug, click on Quick edit then you can see Slug of product.
2. Get WooCommerce product's ID
Login to your WordPress admin > Products > All products.
2. Hover on a product that you want to get the product's ID then you can see the ID of the product.
All the best,
The Ryviu team