Use the DELETED table to access the old values:
DML trigger statements use two special tables: the deleted table and the inserted tables. SQL Server automatically creates and manages these tables. You can use these temporary, memory-resident tables to test the effects of certain data modifications and to set conditions for DML trigger actions.

The deleted table stores copies of the affected rows during DELETE and UPDATE statements. During the execution of a DELETE or UPDATE statement, rows are deleted from the trigger table and transferred to the deleted table. The deleted table and the trigger table ordinarily have no rows in common.

See https://learn.microsoft.com/en-us/sql/relational-databases/triggers/use-the-inserted-and-deleted-tables?view=sql-server-ver15

Hello One way to convert from Oracle to Sql Server could be this:

CREATE TABLE AM_LABELS (
    LABEL_ID int PRIMARY KEY,
    LABEL_NAME NVARCHAR(50)
);

CREATE TABLE AM_LABEL_URLS (
    URL_ID int PRIMARY KEY,
    LABEL_ID int,
    URL NVARCHAR(200),
    FOREIGN KEY (LABEL_ID) REFERENCES AM_LABELS(LABEL_ID)
);

INSERT INTO AM_LABELS (LABEL_ID, LABEL_NAME) VALUES (1, 'Label 1');
INSERT INTO AM_LABELS (LABEL_ID, LABEL_NAME) VALUES (2, 'Label 2');

INSERT INTO AM_LABEL_URLS (URL_ID, LABEL_ID, URL) VALUES (101, 1, 'www.john1.com');
INSERT INTO AM_LABEL_URLS (URL_ID, LABEL_ID, URL) VALUES (102, 1, 'www.john2.com');
INSERT INTO AM_LABEL_URLS (URL_ID, LABEL_ID, URL) VALUES (103, 2, 'www.john3.com');

select * from AM_LABELS
select * from AM_LABEL_URLS

CREATE OR ALTER TRIGGER TRG_DEL_AM_LABELS
ON AM_LABELS
INSTEAD OF DELETE
AS
BEGIN
    DELETE FROM AM_LABEL_URLS WHERE LABEL_ID IN (SELECT deleted.LABEL_ID FROM deleted);
    DELETE FROM AM_LABELS WHERE LABEL_ID IN (SELECT deleted.LABEL_ID FROM deleted);
END;
GO

Test the trigger

DELETE FROM AM_LABELS 
WHERE LABEL_ID=2;

Hope it helps.