Google Spreadsheet ID and Google Sheet ID can be find easily in doc url.

https://docs.google.com/spreadsheets/d/spreadsheetId/edit#gid=sheetId

https://docs.google.com/spreadsheets/d/this-is-spreadsheet-id/edit#gid=this-is-sheet-id

Read more at https://developers.google.com/sheets/api/guides/concepts#sheet_id