Note: In Word 365, it’s possible for you to customize the options on each tab.
If the Page Numbers option is missing from Word, it may have been removed.
From there select Quick Access Toolbar to modify the options available.
If you want to take the easy way, just snag the Reset button.
FAQ
Why are my page numbers not printing?
You may have to adjust the margins.
Select File > Print > Page Setup (at the bottom) > Margins.
Try setting all of the margins to 0.
How can I start page numbering with a specific number?
How can I start page numbering on page 2?
How do I view Page Count?
Under the Review menu, select Word Count.
Statistics will be displayed, including Pages.