It is not at all clear as to what you are trying to achieve...

I take it that you are selling "virtual" products (software downloads)?

Is that right?

And you now want to UPLOAD a whole lot of these "products" to the server?

If this is what you are referring to then the database does not enter into the picture. What are you trying to do with the database?

The ERROR you report says that a folder called "download" is not present. This has absolutely nothing to do with the database. It is a FOLDER (directory) in your root installation, that is being reported as not being there - in your case in public_html/snfcart/download