Sql Server Query taking long time to execute

Hi All,

The below query in SQL server takes long time to execute. I was using this query in SSIS SQL Execute task which also took a lot of time. It ran fine before but now its taking around 2 hrs. Could you guys please help me what can I do to optimize it?

SELECT DISTINCT RIGHT(BizTalk_POA_HEADER.PONUMBER,6) AS PONUMBER,

       Suppliers.SupplierName,
       Company_Details.CompanyName,
       Company_Details.[Email],
       BizTalk_POA_HEADER.[DateDelivery]

       FROM BizTalk_POA_HEADER INNER JOIN
       PO_Details ON RIGHT
       (BizTalk_POA_HEADER.PONUMBER,6) =
       PO_Details.PoNumber INNER JOIN

       PO ON PO_Details.PurchaseOrderID =
       PO.PurchaseOrderID INNER JOIN
       SupplierDetails ON PO.SupplierDetailsID =
       SupplierDetails.SuppliersDetailsID INNER JOIN
       Suppliers ON SupplierDetails.SupplierID =
       Suppliers.SupplierID INNER JOIN
       Company_Details ON PO.CompanyID =
       Company_Details.CompanyDetailsID


WHERE    (RIGHT(BizTalk_POA_HEADER.PONUMBER,6) = '673272')

shivangdesai