Even if you find a planet that is completely identical in chemical composition to the Earth, it is difficult to say what the likelihood of the presence of life on it is. Life on Earth is already the result of some events that happened in the past, we do not know what the probability of these events that led to it was.
To talk about the probability in such cases, you need at least some statistical data. For example, on such and such a percentage of planets with such and such a value of such and such a parameter, life is present. And so on in different ways. Then it will be possible to justifiably declare a certain probability of life on some planet, knowing the values of some parameters.
And what statistics do we have on life on planets? Which sample? With "already" one planet on which we discovered life (and that one is "under our feet"), it is possible to know reliably and reasonably only that it is greater than zero and not greater than one.