The subfields doesnt really have a specific ID.. However you can do a loop counter in your while(has_sub_field()) and use that to create custom ids..
example:
<?php
$i = 1;
while(has_sub_field('myfield')):
echo '<div id="item-' . $i . '">' . get_sub_field('mysubfield') . '</div>';
$i++;
endwhile;
?>
This will give your items an id of item-1, item-2 etc. so in your anchor you can do:
<a href="#item-2">link to second item</div>
