Carousel slider with WP_Query to show 3 posts on each slide

I am trying to create a bootstrap carousel to show 3 posts on each slide. But my code is showing only a single item on each slide.

Here is my code:

            <div class="col-lg-9">
                <div id="popular-services" class="carousel slide" data-ride="carousel">
                    <ol class="carousel-indicators">
                        <!-- Start Carousel Indicator Loop -->
                        <?php if ( $popular_services->have_posts() ) : while ( $popular_services->have_posts() ) : $popular_services->the_post(); ?>
                        <li data-target="#popular-services" data-slide-to="<?php echo $popular_services->current_post; ?>" class="<?php if ( $popular_services->current_post == 0 ) : ?>active<?php endif; ?> text-primary"></li>
                        <?php endwhile; endif; ?>
                    </ol>
                    <?php rewind_posts(); ?>
                    <div class="carousel-inner" role="listbox"> 
                        <?php if ( $popular_services->have_posts() ) : while ( $popular_services->have_posts() ) : $popular_services->the_post(); ?>
                            <div class="carousel-item <?php if ( $popular_services->current_post == 0 ) : ?>active<?php endif; ?>">
                                <div class="row">
                                    <div class="col-lg-4">
                                        <div class="card">
                                            <?php
                                                if ( has_post_thumbnail() ) {
                                                    echo get_the_post_thumbnail($post->ID, 'thumbnail', array('class' => 'card-img-top') );
                                                }
                                            ?>
                                            <div class="card-body">
                                                <?php echo the_title('<h5 class="card-title">', '</h5>'); ?>
                                                <p class="card-text"><?php echo my_custom_excerpt(20); ?></p> 
                                                <?php echo my_custom_read_more('Learn More'); ?>
                                            </div>
                                        </div>
                                    </div>
                                </div>
                            </div>
                        <?php endwhile; endif; ?>       
                    </div>
                </div>
            </div>

What changes do I need to make in order to get it working as per my need.

Thanks in advance.