Haven’t tested it, but should be:
geodirectory/geodirectory-widgets/geodirectory_popular_widget.php
line to be edited:
from
echo ucwords($cat->name).' (<span class="geodir_term_class geodir_link_span geodir_category_class_'.$post_type.'_'.$cat->term_id.'" >'.$total_post.'</span>) ';
to
echo ucwords($cat->name);
If you modify the plugin widget directly you will lose the changes after every new update.
The best thing to do, would be to copy the entire widget code and registration action. Copy the code in your theme functions.php file, rename the class and function name, modify the widget description and update the class name in the register_widget call.
At this point you will have your new popular post category widget in your theme and you can modify it as you wish without having to deal with plugin updates.
Thx