Order of sheets in pages

What app are you talking about?

If it is a word processing document, you cannot simply drag and drop pages to change their order. You can do it with sections but not pages within a section. You can cut & paste text from one place to another but you'll have to do shapes and tables and such (if you have any on the page) separately from the text, you can't select both at the same time. Alternatively you could add section breaks to the end of the first two pages, move everything around, then delete the section breaks (and you might need to add page breaks in their place). Probably easier to cut & paste.

If it is a Page layout document (such as a brochure), you can swap pages by dragging and dropping them. On the toolbar, click on View. Choose to show page thumbnails. You can drag the thumbnails into a different order.