Can anyone help provide CSS code to change only mobile site products to 3 per row? My desktop version is 3 per row now, but changes to 1 on mobile.

Site URL: https://www.ginageiss.com/

specifically it's for this page https://www.ginageiss.com/shop

but it'd also be helpful to get it for this page as well https://www.ginageiss.com/

Shop url doesn't exist

With homepage, try adding to Design > Custom CSS

@media screen and (max-width:640px) {
.thumbnail-layout-basic-grid #projectThumbs .project {
    width: calc(33.333% - 10px) !important;
    margin-right: 5px !important;
    margin-left: 0 !important;
    clear: none !important;
}
.thumbnail-layout-basic-grid #projectThumbs .project:nth-child(3n+1) {
    clear: left !important;
}
}