Several terms are illegal to use when searching Confluence, like : or {. If you search for just the macro term, you're likely not to get the right search results. For example, searching for 'usage', which is the name of a macro but also a common English word, will not yield an accurate count.
Query the Database
If, for example, you want to search for the uses of the usage macro, you can search the database:
For large instances of Confluence, searches across the entire bodycontent table of the database might be environmentally taxing. You can try this on a test server.
You might want to use the SQL Plugin to automate this, or better yet the Macro usage stats plugin. Note that these are third party (unsupported) plugins.
SELECT * FROM BODYCONTENT WHERE BODY LIKE '%{usage}%'
If you want to get the last users or the creators of the pages where the noformat macro is used, you might run:
SELECT CREATOR FROM CONTENT WHERE CONTENTID IN (SELECT CONTENTID FROM BODYCONTENT WHERE BODY LIKE '%{noformat}%') GROUP BY CREATOR
SELECT LASTMODIFIER FROM CONTENT WHERE CONTENTID IN (SELECT CONTENTID FROM BODYCONTENT WHERE BODY LIKE '%{noformat}%') GROUP BY LASTMODIFIER
Listing the occurences of the excerpt include macro (MYSQL only)
select c.contentid, c.title, c.lastmoddate, c.lastmodifier, s.spacename from bodycontent bc join content c on bc.contentid=c.contentid join spaces s on s.spaceid = c.spaceid where c.contenttype='PAGE' and prevver is null and bc.body regexp '.*\{(excerpt-)?include*\}.*';
Logging Uses of a Macro
This information won't tell you how often a macro is invoked, but rather how often it appears on pages. For counting how often it's invoked (and measuring the time it takes to invoke it), check Identifying Slow Performing Macros.