How to turn blog layout 9 into 3 columns

In order to change the layout view into 3 columns navigate to WordPress Dashboard >> Divi >> Theme Builder >> head over to Lucid blog layout >> click on the edit icon (in the Custom Body)

Head over to module named Custom CSS >> click on gear icon >> add below code snippet in the code option of the module.

.lucid-blog-layout .et_pb_post:nth-child(odd) {
  margin-right: 3%;
}
.lucid-blog-layout .et_pb_post:nth-child(even) {
    margin-right: 3%;
}
.lucid-blog-layout .et_pb_post {
  clear: none;
  float: left;
  margin-bottom: 4%;
  padding: 0px;
  width: 30.33%;
}
/* to fix display of the preview on visual builder. */
.et-db #et-boc .et-l .et_pb_ajax_pagination_container {
    display: flex;
    flex-wrap: wrap;
}
.et-db #et-boc .et-l .lucid-blog-layout .et_pb_post {
    margin-bottom: 4%;
}
.lucid-blog-layout div {
    width: 100%;
}
@media(max-width: 767px) {
.lucid-blog-layout .et_pb_post {
  float: inherit;
  margin: 3% 0;
  width: 100%;
  }
}

Output: