Sql Profiler: what does Duration measure for exec sp_execute
The short answer is that the unit description is mentioned in the answer to this question:

https://stackoverflow.com/questions/2590304/unit-of-measurement-for-duration-column-in-sql-profiler

Also, just to add on to Aaron Bertrand's comment, here is some information on why SQL Profiler should be avoided, and what to use instead (at least through SQL Server 2012):

Performance Impact: Profiler Tracing vs. Server Side SQL Tracing, by Linchi Shea

http://sqlblog.com/blogs/linchi_shea/archive/2007/08/01/trace-profiler-test.aspx

Basically, SQL Profiler can have a large impact on the remote server whereas SQL Trace on the server side has much less impact on the remove server.
Google the following phrases for more info:

Server-Side Tracing and Collection

SQL Server Performance Statistics Using a Server Side Trace

Automating Server Side Tracing in SQL Server

How to identify SQL Server performance issues, by analyzing Profiler output?

Good luck.