Classic usage and popularity reports will no longer be available on classic SharePoint online sites after August 7th 2020. From this date, users will be able to find site usage data through the modern Site Usage Report.
On classic sites, the modern site usage report will be available through Site Settings > Popularity Trends > Usage. Data will be available for the last 90 days. The modern Site Usage Report will include data from modern and classic sites and download of data in Excel format will be available.
The modern Site Usage Report page shows a number of key metrics related to site usage.
Unique visitors
Shows the total number of unique visitors to the site and covers access to site content such as pages, documents and news.
Daily user trends are available for last 7, 30 or 90 days.
Site visits
Shows the total number of visits to content such as pages, documents and news for last 7, 30 or 90 days. The site visits report filters out repetitive, continual operations by the same user on the same item so should give a good indication of how popular specific content is.
Average time spent per user
Shows the trend of actual time spent on SharePoint pages and news posts by users. The report calculates the time users are active on the page or news post, ignoring time when the page is minimized or open but inactive. Metrics are available for last 7 and 30 days.
Popular content
Shows the most popular content on the site sorted by site pages, news posts and documents over the last 7 days.
Site traffic
Shows hourly trend of traffic to the site over last 7, 30 or 90 days.
Popular platforms
Shows the devices used to visit the site (Desktop, Mobile web, Mobile app, Tablet) over last 7, 30 or 90 days.
Shows a list of files on the site that have been shared with external users outside of your organisation.
More on viewing usage data for your SharePoint site is available from Microsoft