If you can do the same thing from IEE, use the Debug Console to identify the necessary PL/SQL block to call, and the parameters/values used.

I was able to call the find_part procedure using this:
 

DECLARE
    qty_available       NUMBER := -1;
    location_no         VARCHAR2(60);
    lot_batch_no        VARCHAR2(60);
    serial_no           VARCHAR2(60);
    eng_chg_level       VARCHAR2(60);
    waiv_dev_rej_no     VARCHAR2(60);
    configuration_id    VARCHAR2(60);
    activity_seq        NUMBER := 0;
    handling_unit_id    NUMBER := 0;
BEGIN
    inventory_part_in_stock_api.find_part(
        qty_available,
        location_no,
        lot_batch_no,
        serial_no,
        eng_chg_level,
        waiv_dev_rej_no,
        configuration_id,
        activity_seq,
        handling_unit_id,
        'MX',
        '311-0256-583',
        '*',
        '*',
        '*',
        '*'
    );

    dbms_output.put_line('Quantity Avail = ' || nvl(to_char(qty_available), 'Blank'));
    dbms_output.put_line('Location # = ' || nvl(to_char(location_no), 'Blank'));
    dbms_output.put_line('Lot/Batch No = ' || nvl(to_char(lot_batch_no), 'Blank'));
    dbms_output.put_line('Serial No = ' || nvl(to_char(serial_no), 'Blank'));
    dbms_output.put_line('Eng_Chg_Level = ' || nvl(to_char(eng_chg_level), 'Blank'));
    dbms_output.put_line('Waiv_Dev_Reg_No = ' || nvl(to_char(waiv_dev_rej_no), 'Blank'));
    dbms_output.put_line('Coniguration ID = ' || nvl(to_char(configuration_id), 'Blank'));
    dbms_output.put_line('Activity Sequence = ' || nvl(to_char(activity_seq), 'Blank'));
    dbms_output.put_line('Handling Unit ID = ' || nvl(to_char(handling_unit_id), 'Blank'));

    dbms_output.put_line(serial_no.count);
END;

However, when I tried scrap_part using this:

DECLARE
    catch_quantity      NUMBER := 0;
    contract            VARCHAR2(60) := 'MX';
    part_no             VARCHAR2(60) := '311-0256-583';
    configuration_id    VARCHAR2(60);
    location_no         VARCHAR2(60) := '20642';
    lot_batch_no        VARCHAR2(60);
    serial_no           VARCHAR2(60);
    eng_chg_level       VARCHAR2(60) := '1'; 
    waiv_dev_rej_no     VARCHAR2(60);
    activity_seq        NUMBER := 0;
    handling_unit_id    NUMBER := 0;
    quantity            NUMBER := 1;
    scrap_cause         VARCHAR2(60) := 'MXSCRA01';
    scrap_note          VARCHAR2(60) := '8';

BEGIN
    inventory_part_in_stock_api.Scrap_Part(
        catch_quantity,
        contract,
        part_no,
        configuration_id,
        location_no,
        lot_batch_no,
        serial_no,
        eng_chg_level,
        waiv_dev_rej_no,
        activity_seq,
        handling_unit_id,
        quantity,
        scrap_cause,
        scrap_note
    );

    dbms_output.put_line('catch_quantity = ' || nvl(to_char(catch_quantity), 'Blank'));
END;

I get the error I mentioned.  I’m afraid I don’t know about the debug console.  I used System Info to find the Api and procedure name.

Thank you for suggesting the debug console.  I was able to use that to see I was missing a NUMBER value that needed to be null instead of 0.  I appreciate your quick response!

You can open the Debug Console from one of the top menus in IEE.

Seems we replied at the same time there  

So, one related question.  Is there a way to undo scrapping a part, after a commit?

Thanks in advance.

Sounds like a question that might get a better answer in a supply chain forum, but we will see...