Hi,
After you do the expor,t you want to:
- open the CSV with Excel, or even better, libreoffice calc.
- remove the product_id column
- remove the lines to generate the category tree at the beginning to only keep the first line with the column names and the product lines.
Normally, the categories are linked by their names not their ids so even if the ids are different, if the names are the same, the import system should be able to attach the products to the corresponding categories on the new website.