Creating a After Insert Trigger
You don't need the select:

create or replace trigger insert_record
  after insert on tbl_user_order
  for each row
BEGIN
  insert into retailer_deliver_customer
    (prod_name,product_quantity,message,delivery_date,delivery_address,pin_code)
  values(
    :new.prod_name,
    :new.prod_quantity,
    :new.meessage,
    :new.delivery_date,
    :new.delivery_address,
    :new.pin_id);

end insert_record;
/


You can't commit in a trigger. The actions inside a trigger are always part of the transaction that fired the trigger.