There are lots of questions asking whether there are before triggers in SQL Server. There are nothing called Before Triggers in SQL Server.
What is the requirement for the Before Trigger?
Let us say, you want to verify some values other table before inserting it. In SQL Server, you can use INSTEAD OF TRIGGER.
CREATE TRIGGER tr_data_before ON Table_Data
INSTEAD OF INSERT
SET NOCOUNT ON
IF EXISTS (SELECT 1 FROM Tablle_Data2)
INSERT INTO dbo.Table_Data