Oracle 21c

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CREATE TABLE mytable (
  barcode varchar(20)
);

insert into mytable values
('ABCDEFGHIJKLMNO');
1 rows affected

insert into mytable values
('XXX-XXXX-XXXXXXX-X');
1 rows affected

SELECT barcode,
  SUBSTR(barcode, 1, 3) || '-' || SUBSTR(barcode, 4, 4) || '-' || SUBSTR(barcode, 8, 7) || '-' ||  SUBSTR(barcode, 15, 1) as splitted            
FROM mytable
WHERE barcode NOT LIKE '%-%-%-%' AND LENGTH(barcode) = 15


BARCODE
SPLITTED


ABCDEFGHIJKLMNO
ABC-DEFG-HIJKLMN-O


UPDATE mytable
SET barcode = SUBSTR(barcode, 1, 3) || '-' || SUBSTR(barcode, 4, 4) || '-' || SUBSTR(barcode, 8, 7) || '-' ||  SUBSTR(barcode, 15, 1)               
WHERE barcode NOT LIKE '%-%-%-%' AND LENGTH(barcode) = 15
1 rows affected

select *
from mytable


BARCODE


ABC-DEFG-HIJKLMN-O

XXX-XXXX-XXXXXXX-X