There are a couple of ways to organize the pages in an Azure DevOps Wiki. The easiest method is using the portal and dragging-and-dropping the pages to arrange the better way that fits your needs.
The second method for organizing pages in an Azure DevOps Wiki is using the .order file that can be found in the repo used by the WikiProject. By default, the WikiProject repo is hidden. The only way to access it is by typing this URL.: https://dev.azure.com/<OrganizationName>/_git/<ProjectName>/<ProjectName>.wiki
In the new page, which is a regular repo, change the order of the pages on the .order file. The first line means the first position. Commit the changes, and the result will be the new order defined in the file being applied to the WikiProject. You can see that by refreshing the WikiProject on your web browser.