Hi @Hiteshkumar Patel,
A minimal reproducible example is not provided.
Here is a conceptual solution for you based on tokenization via SQL Server's XML and XQuery functionality. It will work starting from SQL Server 2017 onwards (due to TRIM() function extended functionality).
We will tokenize the Item_Description column as XML. After that we will retrieve 7th token, cast it as integer, and sort by it.
-- DDL and sample data population, start
DECLARE @tbl TABLE (ID INT IDENTITY PRIMARY KEY, Item_Description VARCHAR(200));
INSERT @tbl VALUES
('MATT BOPP FILM [ 20MIC X 575MM ]'),
('MATT BOPP FILM [ 20MIC X 1115MM ]'),
('MATT BOPP FILM [ 20MIC X 1220MM ]'),
('MATT BOPP FILM [ 20MIC X 675MM ]');
-- DDL and sample data population, end
DECLARE @separator CHAR(1) = SPACE(1);
SELECT *
FROM @tbl AS t
CROSS APPLY (SELECT TRY_CAST('<root><r><![CDATA[' +
REPLACE(Item_Description, @separator, ']]></r><r><![CDATA[') +
']]></r></root>' AS XML)) AS t1(c)
CROSS APPLY (SELECT TRY_CAST(TRIM('M' FROM c.value('(/root/r[7]/text())[1]', 'VARCHAR(10)')) AS INT)) AS t2(x)
ORDER BY x ASC;