You would need to use a select field and you can populate the field https://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/
You can also have ACF output the form without form tags
<!-- you need to supply the form tags with all correct attributes -->
<form><!-- add correct attributes to this tags -->
<!-- add a field before or after acf fields -->
<input type="text" name="my-field" value="" />
<?php
// call acf form
acf_form('form' => false);
?>
</form>
