How to select an item from a column only if none of the value in corresponding column is NULL
you can use NOT IN and a subselect


CREATE TABLE modelitem
    ([ltemNumber] varchar(7), [Cornponent] varchar(6), [Quantity] varchar(4))
;
    
INSERT INTO modelitem
    ([ltemNumber], [Cornponent], [Quantity])
VALUES
    ('Modell', 'Wheel', '19'),
    ('Modell', 'Bolt', '19'),
    ('Modell', 'Engine', NULL)
    ,('Modell', 'Engine', NULL),
    ('Model 2', 'Wheel', '19'),
    ('Model 2', 'Bolt', '19'),
    ('Model 2', 'Engine', '6'),
    ('Model 3', 'Wheel', '19'),
    ('Model 3', 'Bolt', '19'),
    ('Model 3', 'Engine', '6'),
    ('Mode14', 'Wheel', '19'),
    ('Mode14', 'Bolt', '19'),
    ('Mode14', 'Engine', '6')
;
GO




SELECT DISTINCT [ltemNumber] FROM modelitem WHERE [ltemNumber] NOT IN (SELECT DISTINCT [ltemNumber] FROM modelitem WHERE [Quantity] IS NULL)
GO


| ltemNumber |
| :--------- |
| Mode14     |
| Model 2    |
| Model 3    |


db&lt;&gt;fiddle here