Since this conviction in a foreign soil has not affected you in any manner in India, what is the necessity for you to disclose or voluntarily eveal them, you may better remain silent because there can be no background verification about this in India.
In general the rule is common for all whether in India or elsewhere.
however since you have not underwent any sentence and moreover this record of conviction has not reflected in any document that are essential and have to be produced before the new employer here in India, you need not voluntarily disclose the facts.
It may not even be consiered as suppression of facts until it is known to them through unscrupulous people who work behind you in India.