The problem: you have a comma separated string that you have to use for a query.

Oracle_String_To_Array_and_Query.sql

DECLARE
  a dbms_utility.uncl_array;
  len PLS_INTEGER;
  input_string STRING(999) := '0099905666,0099905667,0099905668,0099905669';
  my_code STRING(99);
BEGIN
  -- add a letter to make it works
  input_string := 'x' || Replace(input_string,',',',x');
  -- convert the string in an array
  dbms_utility.Comma_to_table(input_string, len, a);
  -- loop that array
  FOR i IN 1..a.count
  LOOP
    -- now we have the single value in a variable
    -- remember to remove the added letter!
    my_code := Substr(A(i),2,99);
    -- and then we can use it in a query (just remember the added letter!)
    FOR cntr IN
    (      SELECT *
           FROM   contracts
           WHERE  contract_code = my_code )
    LOOP
      dbms_output.Put_line( cntr.contract_code );
    END LOOP;
  END LOOP;
END;/

Inspired by https://community.oracle.com/thread/43542