If you’re using a WooTheme then this code may have been utilized in the theme. It will already be pluggable which means you’ll need to redefine the function in your functions.php file (preferably in a child theme) to overwrite the theme default.
/Override theme default specification for product # per row/
function loop_columns() {
return 2; // 2 products per row
}
add_filter('loop_shop_columns', 'loop_columns', 999);
please check LINK for more information :Change number of products per row