If the format is always 3 char followed by 5 numeric can you just get the right 5 characters?
DECLARE @tbSample TABLE(Code VARCHAR(10))
INSERT INTO @tbSample SELECT 'SDH00151'
INSERT INTO @tbSample SELECT 'SDH00152'
INSERT INTO @tbSample SELECT 'SDH00153'
SELECT
Code
,RIGHT(Code,5) AS CodeNum
FROM
@tbSample