Then you’d write a import script to bring that data in from its original source: https://www.datocms.com/docs/import-and-export/importing-data (this is easier if you have access to the original data source, rather than trying to scrape the Next-generated HTML)
This will probably take a few hours or days of work, depending on the complexity of your incoming schema and data. I don’t know what your incoming data looks like, but hopefully the docs can get you started? If you run into trouble along the way, please feel free to reach out for more help If there’s anything sensitive/private, you can always email us at support@datocms.com instead.