The Go To Page feature was not included in Pages v5.2.2. You might consider exporting the Pages document as PDF. Open it in Preview, and from the Preview View menu, Customize Toolbar… Drag/drop the Page item to the Toolbar where it is convenient, and click Done. Now you can directly enter the Page number you want to read. This is visually re-enforced by enabling thumbnails. Jump to a Page number, and the specific Page thumbnail is selected.
Yes, I realize that the above is a discontinuity from the expected word processing convenience that nearly every application but Pages v5.2.2 has incorporated. It is questionable that this glaring omission would have gone unfixed if the product was used with any writing intent within Apple.