I got some requirement to check the site content and structure in SharePoint 2013.i was wondering not able to find the exact place.Then i searched msdn, i got the place where it is located.

The item is no longer in the action menu.

You can reach it from Site Settings --> Content and Structure (under Site Administration)

Site settings -Site administration
Or you can use the url option to find,
http://gauti.sharepoint.com/_layouts/15/sitemanager.aspx
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