the file manager will pass the path and file name of the uploaded file as a part of the post, it will not pass the file extenmsion, you will need custom coding to get the file extension.
to store the path and file name, you will need to edit the insert record server behavior, bind the image database column to the images form element.
use the following code for the value of the extension column:
<?php echo((isset($_POST["images"]))?substr($_POST["images"],-3, 3):"") ?>