Pratik,
There is a ton of information already posted here on CiteHR about experience letters. Use the research box at the top of the page. Other members have discussed this topic many times.
You may not find exactly what you want, but there are enough different formats for you to use as a guide to write your letter.
When you have drafted a letter, if you are not sure, then share it with CiteHR members who can comment, and suggest changes.
You DO NOT have to pay someone to write this letter for you. There is enough information here to assist you.