You will first need to log into your Etsy account, and then navigate to the ‘Settings > Shipping Settings’ screen and click on "Shipping Profiles"

Here you will see a number next to the "Shipping Profile name" under ‘Active Listings’. This number is a link, so right click and choose ‘Open in New tab’, then go to this tab.
If you look at the web address bar in your browser, you will see the address for this page. This address contains the Shipping Template Id Number, as Shipping_Profile_ID