How to show include investment in shares in individual books

Hi,

I had invested in shares around 16 years back but did not show it as an investment in my balance sheet since then. I had paid cash for these shares and do not have any proof of purchase. These share are in my demat account. I would like to know the following things-

1.If i sell these shares will there be any tax implication on this?

2. How can I bring this in my books?

3.won't this be called as a long term gain if I sell it now?

Thanks in advance.