<?php
namespace TestHelloWorldBlock;
class HelloWorld extends MagentoFrameworkViewElementTemplate
{
    protected $_productCollectionFactory;

    public function __construct(
        MagentoBackendBlockTemplateContext $context,
        MagentoCatalogModelResourceModelProductCollectionFactory $productCollectionFactory,
        array $data = []
    )
    {
        $this->_productCollectionFactory = $productCollectionFactory;
        parent::__construct($context, $data);
    }

    public function getProductCollection()
    {
        $collection = $this->_productCollectionFactory->create();
        $collection->addAttributeToSelect('*');
        $collection->setPageSize(3); // fetching only 3 products
        return $collection;
    }
}
?>

$productCollection = $block->getProductCollection();
foreach ($productCollection as $product) {
    print_r($product->getData());
    echo "<br>";
}