Sorry If I confuse you. Yes, first I said my source is SQL and yes the original source is my .txt. I thought it is easy for me to load the data into STG and do SQL to parse that data. Anyway, Below is the "While Loop" that I am using to parse the data.
I couldn't figure it out how can I pull One Batch (One Bath start from source_id = '21' to Next source_id = '21') then I can parse the field one by one and load into my destination tables.

Jon, I am sure now I didn't confuse you more.

  DECLARE @loopA_id INT ,
                @loopA_times INT ,
                    
                @Address VARCHAR(50),
                @CITY     VARCHAR(20),
                @iNVOICE    VARCHAR(200),
                @Sta_id        VARCHAR(20);

   SET @loopA_id = 1;
   SET @loopA_times = 0;

-- Create Loop Tables
   IF OBJECT_ID('tempdb..#ExactMatch') IS NOT NULL
    BEGIN
      DROP TABLE #ExactMatch;
    END;

   CREATE TABLE #ExactMatch
    (
     codA_id INT IDENTITY(1, 1) NOT NULL PRIMARY KEY ,
     sta_id VARCHAR(20),
       );

                    -- Load Loop Table
   INSERT INTO #ExactMatch
      (
                    sta_id
      )
      SELECT DISTINCT
        sta_id
                     FROM SourceTable_EIVA
      WHERE source_id = '21'

                            -- Set Loop Times Variable
   SET @loopA_times = @@rowcount;

   WHILE @loopA_id <= @loopA_times
    BEGIN

      SELECT
                        @Address = e.Address1
                        ,@CITY = e.City
                        ,@iNVOICE = (
                                            SELECT Invoice_Detail FROM SourceTable_EIVA e WHERE e.source_id = '31' --s.sta_id
                                                --OR source_id = '31'
                                    )
                        ,@Sta_id = s.sta_id
      FROM  #ExactMatch s
                INNER JOIN SourceTable_EIVA e ON e.sta_id = s.sta_id
      WHERE codA_id = @loopA_id;

                INSERT INTO DestinationTable_A_Eivav (Invoice#,Address1,City,Sta_id)
                VALUES (@iNVOICE,@Address,@CITY,@Sta_id)

      SET @loopA_id = @loopA_id + 1;
    END;