At this time, the page number of the third page may not be numbered from the first page. Actually, we want the third page to start with "1". At this time, you should first select the page number of page 3, and uncheck "Link to the previous page header" under the "Design" menu (as shown in Figure 2). After selecting a page number, right-click Format Page Number-select Start Page Number, and manually fill in1-OK.
Of course, now you can delete the page number of 1-2, and rest assured that it will not affect the subsequent page numbers, because it has been separated by section break.
You can ask if you don't understand.
Specific operations can also refer to the following video: