// Store ID 2 - default currency EUR, base currency USD
// $product is instance of MagentoCatalogModelProduct
$priceInfo = $product->getPriceInfo();
$price = $priceInfo->getPrice('regular_price')->getValue();

$helper->currencyConvert($price, 'EUR', 'USD');

public function convert($price, $toCurrency = null)
{
    if ($toCurrency === null) {
        return $price;
    } elseif ($rate = $this->getRate($toCurrency)) {
        return $price * $rate;
    }

$basePrice = $product->getPrice();
$currency  = $currencyFactory->create()->load('EUR');
$eurPrice  = $currency->convert($basePrice, 'EUR');

$objectManager = MagentoFrameworkAppObjectManager::getInstance();
$productId = 46;
$product = $objectManager->create('MagentoCatalogModelProduct')->load(productId );
$price = $product->getFinalPrice();
$currency = $objectManager->create('MagentoDirectoryModelCurrency')->load('USD');
echo $currency->convert($price,'EUR');