t, Sql Server - rextester

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CREATE TABLE LinkStockEquipment
    ([Stock ID] varchar(2), [Equipment ID] varchar(2), [Equipment Qty] int)
;
    
INSERT INTO LinkStockEquipment
    ([Stock ID], [Equipment ID], [Equipment Qty])
VALUES
    ('A1', 'E1', 5),
    ('A1', 'E2', 3),
    ('A2', 'E3', 4),
    ('A2', 'E4', 6),
    ('A3', 'E5', 2)
;

WITH tmpResult as (
    SELECT 
         [Stock ID],
         'Equipment ID ' + CAST(rn AS VARCHAR(16)) as lblEq,
         [Equipment ID],
         [Equipment Qty]
    FROM ( SELECT *, row_number() over (partition by [Stock ID] ORDER BY [Equipment ID]) as rn
           FROM LinkStockEquipment ) as rows
)    
SELECT [Stock ID], 
       MAX( CASE WHEN lblEq = 'Equipment ID 1' THEN [Equipment ID]  END) as [Eqp ID 1],
       MAX( CASE WHEN lblEq = 'Equipment ID 1' THEN [Equipment Qty] END) as [Eqp Qty 1],
       MAX( CASE WHEN lblEq = 'Equipment ID 2' THEN [Equipment ID]  END) as [Eqp ID 2],
       MAX( CASE WHEN lblEq = 'Equipment ID 2' THEN [Equipment Qty] END) as [Eqp Qty 2],
       MAX( CASE WHEN lblEq = 'Equipment ID 3' THEN [Equipment ID]  END) as [Eqp ID 3],
       MAX( CASE WHEN lblEq = 'Equipment ID 3' THEN [Equipment Qty] END) as [Eqp Qty 3]
FROM       tmpResult
GROUP BY [Stock ID];

View schema
Execution time: 0,01 sec, rows selected: 3, rows affected: 5, absolute service time: 0,24 sec, absolute service time: 0,24 sec