Error saying Conversion failed when converting date and/or time from character string. : SELECT CONVERT(DATETIME,(RIGHT(b.dob,4)+'-'+SUBSTRING(b.dob,3,2) +'-'+LEFT (b.dob, 2)),111) FROM [Load].[123_Qualification] AS b

The Dob is a nvarchar field,and i want it to convert to DateTime Format, but I am  getting an error saying that Conversion failed when converting date and/or time from character string.