The solution above worked but going to the next step, the Payment step, it will mess up the Confirmation time.
To make the order later time into the 12 hour format, you will have to go to to main/views/themes/themeyourusing/checkout.php
From there, you have to change lines 148, 150, 159, 161, under<div class="col-xs-12 col-sm-6 order-later time-input-addon">.
Line 148 <option value="<?php echo $hour; ?>" selected="selected"><?php echo mdate('%h', strtotime($date.' '.$hour.':00')); ?>:</option>
Line 150 <option value="<?php echo $hour; ?>"><?php echo mdate('%h', strtotime($date.' '.$hour.':00')); ?>:</option>
Line 159 <option value="<?php echo $minute; ?>" selected="selected"><?php echo mdate('%i', strtotime($date.' '.$hour.':'.$minute)); ?></option>
Line 161 <option value="<?php echo $minute; ?>"><?php echo mdate('%i', strtotime($date.' '.$hour.':'.$minute)); ?></option>
Here's an image if anyone needs to see it: https://imgur.com/a/qKNyiSh
Thanks so much to @sampoyigi for helping me with this.