How can we know that an Aatma got Moksha?
No there isn't any way to identify that one got mokshya or not as no one has any idea about how the atma is(as its so small as mentioned below and no ordinary human being can see it without the help of supreme Lord) and whose atma it is, only paramathma knows about it.
When the upper point of a hair is divided into one hundred parts and again each of such parts is further divided into one hundred parts, each such part is the measurement of the dimension of the spirit soul.
Source : Śvetāśvatara Upaniṣad (5.9)
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