What should I do if they don't want to give me a Gratuity? October 30, 2017 to 15th October 2022

Dear sir, I would like to inform you that, sir I'm Arindam - an employee of an Organisation since October 30, 2017. My last date in this Organization is 15th October 2022. Could you please tell me if I am eligible for Gratuity? What should I do if they don't want to give me a Gratuity? Please tell me.

According to your service period (Oct 2017 - October 2022) you are eligible to receive payment of gratuity. You may speak to them and a request letter be given to your company for payment,
and wait for a reasonable time. If your company does not respond or if you have not received your gratuity, you can file a complaint against company to the Controlling Authority. But ensure you receive your F&F dues and other statutory dues from the company, before you lodge the complaint against the company

I think your worry is because you have not finished 5 years
This topic has been discussed many many times on the forum, I suggest you read those and then decide.

Just out of curiosity, why couldn't you wait for 15 days more in order not to have a stress on the matter? It would be simple to resign after completing 5 full years, right?

You are eligible for gratuity.. Draw your concern with management to awake them.