Hii Deepak!
Although you didn't mention the name of the examination which you are going to attempt but i assume it's neet as you are asking the code and neet application process is going on in present.
As a third year student you haven't completed your BSc yet, so you will choose - Code 5 as for now. You can refer the following link below  for more details-

https://medicine.careers360.com/articles/neet-qualification-codes
Hope this helps.
Good luck!