Add style on index.vue

index.vue

<style lang="scss" scoped>
/*
 * Card Columns Masonry - Bootstrap 4
 * https://codepen.io/JacobLett/pen/oZmWdd
 */
/* Medium devices (tablets, 768px and up) The navbar toggle appears at this breakpoint */
@media (min-width: 768px) {  
  .card-columns {column-count: 3;}
}

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) { 
 .card-columns {column-count: 3;}
}
 
/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {  
   .card-columns {column-count: 3;} 
}
</style>