instead of using <img src="<?php the_field('brand_logo', $term); ?>" /> you would need to do something like
$image_id = get_field('brand_logo', $term, false); // 3rd arg set to false to ensure we get unformatted value (ID)
// $size is a defined image size
// see https://developer.wordpress.org/reference/functions/wp_get_attachment_image_src/
$image = wp_get_attachment_image_src($image_id, $size);
?>
<img src="<?php echo $image[0]; ?>" />
<?php
