.

 Add below in your active themes's functions.php file

add_action ('init', 'change_columns');
function change_columns() {
    add_filter( 'loop_shop_columns', 'custom_loop_columns' );
    
    function custom_loop_columns() {
        return 3;
    }
}

Then you need to change the width of the columns in CSS, by adding this to your custom CSS area in the WordPress Customize under the Appearance menu.

ul.products li.product { clear: none; width: 30%; }