How to convert varchar to datetime in Sql server database

Question

SELECT [BillNo],[BillDate],[Pts_Name],[Drs_Name],[Medi_Name],[BatchNo],[ExpDt],[MRP]

,[Qty],[Amount] FROM [MEDIDATANEW].[dbo].[CustBill]where (convert (datetime ,convert(datetime,convert(varchar,BillDate,103),103))between '2014-03-12' and '2014-03-23')

 

 

This script run in sqlserver 2008 But Not Run in sqlserver 2008R2 and upper version.

 

plz Help me