Or in any of the other 11 Wordpress tables. I also need to store: submission date, name, contact number in the same table.
What approach would be best? A custom table or using a standard table?
If it's information that logically belongs to a post/page - you store it in
update_post_meta function). If it's something that pertains to a user -
usermeta table is for you. More still, there's Settings API in case you have a plugin that needs to persist any settings.
From your question it is somewhat unclear which of these would be best for you. What's a "submission date"? The name and contact number, I'm guessing, are for a user, and so would belong in the
update_user_meta is a good place to start.