<div class="row">
<div class="col-md-3">
<div class="item"></div>
</div>
<div class="col-md-3">
<div class="item"></div>
</div>
<div class="col-md-3">
<div class="item"></div>
</div>
<div class="col-md-3">
<div class="item"></div>
</div>
</div>
if( have_rows('parent_field', $ID) ):
while ( have_rows('parent_field', $ID) ) : the_row();
$sub_value = get_sub_field('sub_field');
// Do something...
endwhile;
else :
// no rows found
endif;