def make_auxfilenames(list_iter: list, case_name: str, aux_ext: str) -> list:
    """Create a TRACE files with customized extension (used as auxiliary files)

    :param list_iter: (list) the iterator converted to a list of integer
    :param case_name: (str) the case name
    :param aux_ext: (str) the extension of auxiliary file
    :return: list of string with auxiliary filenames according to the iterator
    """
    aux_filenames = []

    for i in list_iter:
        aux_filename = "{}-run_{}{}" .format(case_name, i, aux_ext)
        aux_filenames.append(aux_filename)

    return aux_filenames