1. Right-click on the tab (left below) that you want to copy and choose: Move or Copy….
2. Select (below): Create a copy.
3. Above, under "To book", click on the arrow and choose: New book.
4. Click Ok.
A new workbook opens with the copied sheet on Sheet1; give the new workbook a name and save it.
When you press and hold the Ctrl-button, you can select and copy more than 1 sheet at a time to the same new workbook.