ReferenceError: "Sheets" is not defined
This an advanced service from google. You need to enable this service before using it.https://developers.google.com/apps-script/guides/services/advancedIn the script editor, select Resources > Advanced Google services....In the dialog that appears, click the on/off switch next to the service you want to use.At the bottom of the dialog, click the link for the Google API Console.In the console, click into the filter box and type part of the name of the API (for example, "Calendar"), then click the name once you see it.On the next screen, click Enable API.Close the API Console and return to the script editor. Click OK in the dialog. The advanced service you enabled is now available in autocomplete.
Just add the required service from here, in your case you need Google Sheets API. Good luck.