I don't like the use of a scalar function, but this might help.

DECLARE @m NVARCHAR(max)= N'\u0633\u0644\u0627\u0645';

WITH
E(n) AS(
  SELECT n FROM (VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0))E(n)
),
E2(n) AS(
  SELECT a.n FROM E a, E b
),
E4(n) AS(
  SELECT a.n FROM E2 a, E2 b
),
cteTally(n) AS(
  SELECT TOP(LEN(@m)/6) ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) * 6 n
  FROM E4
)  
SELECT CAST( master.dbo.fn_cdc_hexstrtobin( '0x'
   + (
     SELECT SUBSTRING( @m, n-1, 2) + SUBSTRING( @m, n-3, 2)
     FROM cteTally
     FOR XML PATH(''),TYPE ).value('(./text())[1]','NVARCHAR(MAX)')) AS nvarchar(MAX)) AS STR_VAL;