Install pg_trgm in PostgreSQL 8.4 on Windows XP
Answered in comments by a-horse-with-no-name:

Those are only &quot;notice&quot; message, not errors (I don't understand what they say, but NOTICE is never a problem or even an error). All statements ran without error, so everything is fine and the module was created. But you should really upgrade to a modern version (12 or 13) and also ditch Windows XP.