Hi shubh103.
To score 35+ in verbal, you need to get around 70 percent of the verbal questions correct. So, of the 30 counted verbal questions, you need to get about 21 or 22 correct, or you could go with the idea that you need to get about 25 or 26 of the questions in the verbal section correct.
Regarding how to get to 35+ from 31, you may need to do any of the following:
- learn more SC rules and concepts
- learn better strategies for answering the types of questions you don't commonly get correct currently
- do more untimed practice to learn to see more of what's going on in the questions and execute better
For in-depth discussion of key things you can do to increase your verbal score, see the following posts, each of which focuses on a different aspect of mastering GMAT verbal.
How to Score High on GMAT VerbalThree Key Practice Tips for Mastering GMAT VerbalHow to Get Faster at GMAT Verbal