How much salary should I (19m)ask for?

This was my first internship and it’s about to end it was of three months and now I will be getting an employment letter from the company. It’s a PR company which handles public relations of financial companies or MNCs. Initially, they told me that I would be getting between 18 to 22K after reviewing my performance. Also I’m a part of the team which handles one of the biggest clients of company so there is a lot of work to do for them compared to other clients like clothing brands, hospital etc. as it’s a financial company. also, I was solely hired because of my knowledge about equity markets and stocks. As an intern, I’m getting 8K per month but I am a little confused, How much should I ask for a salary in hand?