How do we know if this is the last Janma? What planet indicates Moksha?

Sorry, but this is not the last janma for anyone who is presently living on the planet Earth- no exception!
It is because the era that we are presently living in is ‘Kalyug’. This era is not fit for going to moksha directly from here.
Mahavideh Kshetra is the place from where moksha can take place.

From here, one has to take at least one more birth as a human being elsewhere. And if this birth happens to be in the Mahavideh Kshetra, then yes, from there we can go to moksha in that very birth, provided we have cleared all our karmas.

Where is Mahavideh Kshetra?
In the universe, there are fifteen worlds where human beings can take birth and live. The fifteen worlds comprise of:
five Bharat Kshetra,
five Airavat Kshetra, and
five Mahavideh Kshetra.

Ours is one of the five Bharatkshetras. There are fourteen other locations where there are human beings just like us. However, the atmosphere between the different worlds is such that it is not possible for one to go from one world to another, unless after death upon reincarnation.

The Mahavideh Kshetra, that is closest to our particular Bharat Kshetra, lies in the northeast direction. And it has on it, Simandhar Swami, as the Living Tirthankar!!!
Without a Tirthankar, our Moksh cannot happen!

In Mahavideh Kshetra, the era of Kalyug never happens! Hence, Tirthankaras are always present there, at all times, whereas here, in our Bharat Kshetra and in Airavat Kshetra, Tirthankaras are born only during a certain period of the time cycle, when Satyug is prevalent.

So, presently there are no Tirthankaras in any of the five Bharat Kshetras or the five Airavat Kshetras. Here, Tirthankaras will come into being during the third and the fourth segment of the next time-cycle now.
Simandhar Swami is the Living God, residing in Mahavideh Kshetra

Yes, Tirthankar Bhagwan Simandhar Swami is living and is present today in the Mahavideh Kshetra, that lies in the northeast direction and is closest to our planet. Also, Simandhar Swami has a subtle bond with our planet! Thus Mahavideh Kshetra is the place from where we can go to Moksha presently.

How to worship Simandhar Swami?
Param Pujya Dada Bhagwan, the Enlightened being, has done the biggest grace on our Bharat Kshetra, by linking the spiritual aspirants with Lord Simandhar Swami.

He advises that we do darshan of the idol of Simandhar Swami, bow down before Him with reverence, and say, "With Dada Bhagwan as my direct witness, I hereby pay my highest obeisance to the Tirthankar Lord Shri Simandhar Swami, present in Mahavideh Kshetra.” While reciting these words, the aspirant experiences the live obeisance to the Lord.
That’s the great connectio
Param Pujya Dadashri has enabled for we people staying in the Bharat Kshetra.

This worship of Simandhar Swami is not done for obtaining any worldly gains. We do darshan and pay obeisance to ‘this greatest being’ with the objective to renounce our weaknesses of anger, pride, deceit, greed and attachment and get liberated just like Him. So, if we have the idol of Simandhar Swami at our home, every time we see Him, we can worship Him with the intent that we soon reach Him, and with His grace, attain the Absolute stage of the Soul.
As one’s devotion towards Lord Simandhar Swami increases, our connection with Him will continue to grow. Eventually this bond becomes so strong that one reaches the feet of the Lord in His next life.

How can we go to Mahavideh Kshetra?
One, our sincere devotion for Simandhar Swami binds merit karmas of the highest order which can take us to Mahavideh Kshetra.

And secondly, after receiving Gnan (Self-Realization) from Gnani, the Enlightened One, in this life, as we follow the Gnani’s given instructions, we are able to finish our worldly interactions here, in Bharat Kshetra with inner meditation, that is devoid of anger pride, greed or deceit. That gives us a reward (merit karma) that takes us to Mahavideh Kshetra.

To conclude,
Lord Simandhar Swami is present in Mahavideh Kshetra for the liberation of all mankind, and to make us reach to Lord, Gnani is present here, amidst us in the Bharat Kshetra, who protects us, prepares us and takes us all the way there to the Mahavideh Kshetra!

Now, our deep inner intent is the only thing that is required i.e. a pure desire to meet Gnani, surrender in his feet, follow his instructions and soon reach Simandhar Swami, where, we all can attai
Moksha.

To know more:
https://www.dadabhagwan.org/path-to-happiness/spiritual-science/moksha/