Hi there @ngthanhdo
The Google Merchant Center helps you sync your store and product data with Google and makes the information available for both free listings on the Shopping tab and Google Shopping Ads. That means everything about your store and products is available to shoppers when they search on a Google property. For reference, linked here is the related documentation.
To be clear, I have 2 separate files for free listing and for running ads
As I understand, you want to run both Free Listings and Smart Shopping campaigns at the same time.
Yes, you can run both at the same time, and we recommend it! In the US, advertisers running free listings and ads together have seen an average of over 50% increase in clicks and over 100% increase in impressions on both free listings and ads on the Shopping tab. Your store is automatically opted into free listings automatically and can choose to run a paid Smart Shopping campaign.
Feel free to check out this page, detailing how you can get the most out of your Smart Shopping campaign.
I trust that points you in the right direction, but if you have more questions, let us know. We’re happy to help.