initial_df = pandas.read_csv('your_file_path')
final_df = pandas.concat([Series(row['Order ID'], row['Items Ordered'].
    split(',')) for _, row in initial_df.iterrows()]).reset_index()
final_df
final_df.columns = ['Items Ordered', 'Order ID']
final_df
final_df[['Order ID', 'Items Ordered']]
Pandas - split column stored as csv