1) I Assume you have created Model and Collection file associated with that tables.
2) In a Block PHP file constructor add one argument (Dependency Injection) like below and store it in a class member variable.
public function __construct(
Context $context,
\Namespace\Modulename\Model\ModelNameFactory $modelNameFactory,
array $data = array()
) {
$this->_modelFactory = $modelFactory;
parent::__construct($context, $data);
}
3) Prepare a public method in your block to access collection like below.
public function getCollection(){
return $this->_modelFactory->create()->getCollection();
}
4) Loop through each of the collection result.
Hope, this will help you.