Access the report via Analytics Cockpit - Search Report
The Search Report consists of
a graph showing the overall number of searches over the selected timeframe (default: last 30 days)
a table listing
search terms: what your users inserted into the search field.
number of results: how many results Confluence found for that particular search term.
number of searches: how often users carried out this particular search.
Click on the "Settings" button on the Search Report. Here, you can specify
the minimum length of a search term
if numbers in searches should be included or ignored.