SQL Server 2019

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DECLARE @TABLE_A AS TABLE
(
   [Start] varchar(20),
   [End] varchar(20),
   [Qty] numeric(10)
)

DECLARE @TABLE_B AS TABLE
(
   [Start] varchar(20),
   [End] varchar(20),
   [Qty] numeric(10)
)

INSERT INTO @TABLE_A VALUES('ABC001','ABC005',5)
INSERT INTO @TABLE_A VALUES('ABC007','ABC007',1)
INSERT INTO @TABLE_A VALUES('AC0002','AC0003',2)

;WITH CTE  AS (
	SELECT SUBSTRING([Start],0,PATINDEX('%[0-9]%', [Start])) as prefix,
		   CAST(SUBSTRING([Start],PATINDEX('%[0-9]%', [Start]),LEN([Start]) - PATINDEX('%[0-9]%', [Start]) + 1) AS INT) fromNum,
		   CAST(SUBSTRING([End],PATINDEX('%[0-9]%', [End]),LEN([End]) - PATINDEX('%[0-9]%', [End]) + 1) AS INT) toNum,
		    PATINDEX('%[1-9]%', [Start]) - PATINDEX('%[0-9]%', [Start])  paddingOfZero
	FROM @TABLE_A
	UNION ALL
	SELECT  prefix,
			fromNum +1,
	        toNum,
			paddingOfZero
	FROM CTE 
	WHERE fromNum +1<=toNum
) 
INSERT INTO @TABLE_B ([Start],[End],Qty)
select CONCAT(prefix,FORMAT(fromNum,REPLICATE('0',paddingOfZero + 1))),
	   CONCAT(prefix,FORMAT(fromNum,REPLICATE('0',paddingOfZero + 1))),
	   1
from cte

SELECT *
FROM @TABLE_B

Start	End	Qty
ABC001	ABC001	1
ABC007	ABC007	1
AC0002	AC0002	1
AC0003	AC0003	1
ABC002	ABC002	1
ABC003	ABC003	1
ABC004	ABC004	1
ABC005	ABC005	1