Trigger question

How do i write an convert an Oracle trigger to Microsoft sql server

Oracle trigger:
CREATE OR REPLACE TRIGGER zip_modify_oracle
AFTER INSERT OR UPDATE
ON Orders
FOR EACH ROW
BEGIN
-- Find ZIP_CODE
IF :new.ZIP_CODE is NULL then
:new.ZIP_YN = 0;
else
:new.ZIP_YN = 1;
END IF;
END;

Microsoft SQL sERVER:
CREATE TRIGGER zip_modify_mirosoftsqlserver
ON Orders
FOR INSERT,UPDATE
AS
???

CAN ANYONE HELP?