How do I start my career at 31 with an M.Com (CA) degree and no prior work experience?

Ans: Hi!!
Congratulations ...you took care of your children when they were young, and now that they are all grown up you want to take up a job!!
You are just 31 yrs old, you are still so young, some advantages of marrying early. Now is that time to learn, relearn, and unlearn....find out what is that you love to do the most now which can help you earn money as well. Ask yourself what is that you want to do with your degrees, your life? Find your Ikigai....
Explore the convergence of Ikigai's four primary elements: what you love (your passion), what the world needs (your mission), what you are good at (your vocation), and what you can get paid for (your profession). Take time to reflect and design your life.
Think on this before you get into the job market, you'll be sorted for life...take your time, don't be in a hurry to just get a job. I repeat again here...learn, unlearn and relearn, be prepared before you jump into a job market.

This was my answer to your statement," i dont know how and where to start my career".

Hope this helps... all the very best for your future!!