var swiper = new Swiper('.swiper-container', {
    effect: 'fade',
    pagination: {
        el: '.swiper-pagination',
        type: 'fraction',
        formatFractionCurrent: function (number) {
            return ('0' + number).slice(-2);
        },
        formatFractionTotal: function (number) {
            return ('0' + number).slice(-2);
        },
        renderFraction: function (currentClass, totalClass) {
            return '<span class="' + currentClass + '"></span>' +
                   ' - ' +
                   '<span class="' + totalClass + '"></span>';
        }
    },
});

.swiper-container {
    width: 100%;
    height: 100px;
}

.swiper-slide {
    text-align: center;
    font-size: 18px;
    background: #fff;
    background: gray;

    /* Center slide text vertically */
    display: -webkit-box;
    display: -ms-flexbox;
    display: -webkit-flex;
    display: flex;
    -webkit-box-pack: center;
    -ms-flex-pack: center;
    -webkit-justify-content: center;
    justify-content: center;
    -webkit-box-align: center;
    -ms-flex-align: center;
    -webkit-align-items: center;
    align-items: center;
}

<script src="https://unpkg.com/swiper/swiper-bundle.min.js"></script>
<link href="https://unpkg.com/swiper/swiper-bundle.min.css" rel="stylesheet"/>

<!-- Swiper -->
<div class="swiper-container">
  <div class="swiper-wrapper">
    <div class="swiper-slide">Slide 1</div>
    <div class="swiper-slide">Slide 2</div>
    <div class="swiper-slide">Slide 3</div>
    <div class="swiper-slide">Slide 4</div>
    <div class="swiper-slide">Slide 5</div>
    <div class="swiper-slide">Slide 6</div>
    <div class="swiper-slide">Slide 7</div>
    <div class="swiper-slide">Slide 8</div>
    <div class="swiper-slide">Slide 9</div>
    <div class="swiper-slide">Slide 10</div>
  </div>
  <!-- Add Pagination -->
  <div class="swiper-pagination"></div>
</div>

https://stackoverflow.com/questions/56044414/change-the-digit-format-pagination-in-the-slider