>In my Access query I was using IIf statement, now SQL doesn't like that. How I can replace it ?

Check out CASE: (edited this sample from the docs)

SELECT Category = 
        CASE type
            WHEN 'popular_comp' THEN 'Popular Computing'
            WHEN 'mod_cook' THEN 'Modern Cooking'
            ELSE 'Not yet categorized'
        END
FROM myTable

HTH