Shalom and thank you for your question!

You would like to ascertain what your father’s Hebrew name is, in order to name your niece’s child when the time comes, G-d willing.. This is indeed very important, since a person’s Hebrew name is like a spiritual ‘formula’ for the person. One’s spiritual life-force comes through the name.  If your father is still alive, he can be given a Hebrew name.

When people asked the Lubavitcher Rebbe for advice concerning choice of names, the Rebbe would sometimes advise changing the person’s name, and sometimes just to add a Hebrew name.  Since the name parents choose is by Divine Providence, even a name which is not Hebrew, the Rebbe advised that the Hebrew name to be added should bear some similarity in sound or meaning to the original name.

There are many examples, such as Samantha becoming Sarah, John becoming Yonatan, or Neil becoming Nachum.

May there be good news with the birth!