How to view the visitors previous url ?

If you mean a visitors referrer, you can see it in Matomo Analytics > Reporting > Acquisition > Websites page. It will look something like this: https://demo.matomo.cloud/index.php?module=CoreHome&action=index&idSite=1&period=day&date=yesterday#?idSite=1&period=day&date=yesterday&category=Referrers_Referrers&subcategory=Referrers_SubmenuWebsitesOnly

That is correct. Those visitors are counted as “Direct Entries” and the count is shown in the Acquisition Overview and All Channels pages.