Magento: Convert Price from Current Currency to Base Currency

magento.php

<?php
$baseCurrencyCode = Mage::app()->getStore()->getBaseCurrencyCode(); 
$currentCurrencyCode = Mage::app()->getStore()->getCurrentCurrencyCode();
$price = 200;
 
 
// convert price from base currency to current currency
$priceTwo = Mage::helper('directory')->currencyConvert($price, $baseCurrencyCode, $currentCurrencyCode); 
 
 
//convert price from current currency to base currency
 
$allowedCurrencies = Mage::getModel('directory/currency')->getConfigAllowCurrencies();
$rates = Mage::getModel('directory/currency')->getCurrencyRates($baseCurrencyCode, array_values($allowedCurrencies));
// the price converted
$price=$price/$rates[$currentCurrencyCode];
print $price;

which is the filename and position to put this code to convert the currency kindly help me