How to display the date as mm/dd/yyyy hh:mm Am/PM using sql server 2008 r2?

I think there is no single format to give them both. Try this using Convert; Sql-Demo

declare @mydate datetime = getdate()
select convert(varchar(10),@mydate, 101) + right(convert(varchar(32),@mydate,100),8)

|           COLUMN_0 |
----------------------
| 02/22/2013  9:36AM |

The FORMAT() function is available from version 2012 onwards. Once upgraded, you can use

select FORMAT(@date,'MM/dd/yyyy hh:mm:s tt')