Anders from the Shopify Social Care team here. Hope you're doing well!
To update the link found in this section of the Cart page, this can be done in the language section found in the Themes tab (Online Store > Themes > Customize > Edit Languages). On the language edit page, search Continue browsing HTML, and under Cart, you'll be able to update the URL with a product, collection or page like so:
We also have a guide on this process here.
Let me know if you run into any troubles!