OldDog39 on "Add query from spreadsheet table."

1. How do I organize WP and MySQL folders so that they make sense and can be found easily. Some folders are similar.
2. I have a table with 796 rows and 53 columns. I only want 6 to appear on the website but will need a link back to each row so my customers can see the full description of the selected item.
I have installed the TablePress plugin but it only accepts three formats and .sql is not one of them.
3. Where do you modify code, when necessary, for each section of the theme.