Tag manager will let you connect to google ads for conversion tracking etc.
You will also need this -https://market.x-cart.com/addons/google-product-feed.html to generate a product feed for your merchant center.
A detailed guide on how to configure the Google shopping groups in the X-Cart, please check it here: https://kb.x-cart.com/modules/google_product_feed.html#configuring-google-shopping-groups
I have also specified feed rules in google to optimize the ad campaign.
Note: Apologies this is for version 5.x I will still leave it here for others.