I am in support role in an outdated technology, I want to switch but no idea that I should learn Developement course like MERN or Java or get into Data science field?

Don't enroll and fall into trap of costly online boot camps. Rather learn from Udemy, O'Reilly, LinkedIn Learning, Microsoft Learn.

Enter the field of IOT, Blockchain, Machine Learning, Data Science, Generative AI.

I tcs udemy complete krish naik courses. You will complete ML and DL. For Gen AI youtube is good enough.

Also, Cyber security is another promising area.