Add dotted border around all block rows in a section

Example I'm trying to replicate, see purple dots in second section that create a border around all of the block rows within that Wordpress page: https://teachingideas4u.com/free-social-studies-guide (not shown in screenshot is bottom border but it's there if you go to the page itself)

My site is: 
Website:   https://nonagon-blackbird-dbdy.squarespace.com/
           PW:   sscommunityhelp062723

Page I'm trying to do this on is: https://nonagon-blackbird-dbdy.squarespace.com/free-social-studies-guide

#collection-64a2c28eb8d18000905e4af1
.page-section:nth-child(2) .content {
    width: 100%;
    border: 2px solid;
    padding: 27px;
border-width: 10px;
    border-style: dotted;
    border-color: #9438b9;
}

Sadly (because you'll have to recreate the section), the best way for you to do this is to use a "Classic Editor Section":
https://support.squarespace.com/hc/en-us/articles/360027987711-Page-sections#toc-classic-editor

Once you add a new classic section and the content in again, the above CSS should work for that section.