Formatting custom file field

-- url of the page with the problem -- : shower-trays-direct.under-development.in...slate-effect-800x800
-- HikaShop version -- : 4.3.0
-- Joomla version -- : 3.9.19

Hello,
I have a series of custom fields, one of which is a link to a file for installation dimensions. This is a file that can be freely downloaded no matter if a product has been purchased. I understand I could use the Files option on the Product but this is being used for another PDF and displayed in another location on the page. If you look at:

shower-trays-direct.under-development.in...slate-effect-800x800

Under the Specifications tab is where I am displaying the custom fields (from Barcode down) one of this is Dimensions. However I cannot find where I can modify the php loop in the show_block_custom_main.php file so that when it is displaying the file field I can modify the CSS to not simply display the file name but to show a button or similar to the one found on the Instructions tab (this is where the product file is being shown)

Where are the files that control the display of the custom field depending on what type of field it is?

I had tried to use this method:

<span id="hikashop_product_custom_name_<?php echo $oneExtraField->field_id;?>" class="hikashop_product_custom_name">
   <strong>Barcode:</strong><br /><?php echo $this->element->barcode; ?>
</span>
<span id="hikashop_product_custom_name_<?php echo $oneExtraField->field_id;?>" class="hikashop_product_custom_name">
   <strong>Colour / Finish:</strong><br /><?php echo $this->element->colour_finish; ?>
</span>
<span id="hikashop_product_custom_name_<?php echo $oneExtraField->field_id;?>" class="hikashop_product_custom_name">
   <strong>Shape:</strong><br /><?php echo $this->element->shape; ?>
</span>

<span id="hikashop_product_custom_name_<?php echo $oneExtraField->field_id;?>" class="hikashop_product_custom_name">
    <strong>Dimensions:</strong><br /><a href="/media/com_hikashop/upload/safe/<?php echo $this->element->dimension_file; ?>">link</a>
</span>

Nicolas,
Thanks for the reply, but not sure I understand. Do I add and amend the code running in the loop of custom fields?

Currently the code I have above has replaced the php loop of the original template file.

Can I 'revert' to the original template file and simply replace this one line? What happens to the other fields that are not files? I do not want them to render as links?

Nicolas,
Thanks for the help and support most appreciated. I've developed and taken your code and the template a little further!

Probably not the greatest bit of PHP but I need a different value instead of the filename value so I've modifed the code to be:

defined('_JEXEC') or die('Restricted access');
?><?php
$this->fieldsClass->prefix = '';
$displayTitle = false;
ob_start();
foreach ($this->fields as $fieldName => $oneExtraField) {
	$value = '';
	if(empty($this->element->$fieldName) && !empty($this->element->main->$fieldName))
		$this->element->$fieldName = $this->element->main->$fieldName;
	if(isset($this->element->$fieldName))
		$value = trim($this->element->$fieldName);
	if(!empty($value) || $value === '0' || $oneExtraField->field_type == 'customtext') {
		$displayTitle = true;
	?>
// Set$value if a PDF filename to generic text
<?php
  $mxdimensionspdf = $this->fieldsClass->show($oneExtraField,$value);
        if (preg_match('/\pdf\b/', $mxdimensionspdf)) {
    $value = '&nbsp;Dimensions';
}     
?>
		<span id="hikashop_product_custom_name_<?php echo $oneExtraField->field_id;?>" class="hikashop_product_custom_name">
			<?php echo $this->fieldsClass->getFieldName($oneExtraField).':<br />'; ?>
            <?php echo str_replace('target="_blank" class="', 'target="_blank" class="btn btn-info', $this->fieldsClass->show($oneExtraField,$value)); ?>
            
		</span>
	<?php
	}
}
$specifFields = ob_get_clean();
?>
<?php echo $specifFields; ?>

Well that code actually fails, it creates a different URL tot he document that then does not load?

How can I set a 'standard' text value for the button when it is link?

Nicolas,
Apologies for the confusion, yes I want to change the returned HTML of the file, currently it is showing the file name between the <a></a> tags which is not very nice, I want to have a standard piece of text that replaces the file name.

Forgive me what is str_replace? how can I implement this to change the filename?

Thanks again

Nicolas,
I'm forever indebted to you for your time and help. Thanks for sending the code, I'm just about understanding what it is doing, but my PHP knowledge is limited!

I have tried that code but it does not seem to work? Do I have to remove the hastags? What do the hastags mean?

Thanks