The verb you are looking for is "jan-a". The dictionary will likely tell you, it means "to know". However, there is more to it than that. It does mean "to know", i.e. "to possess knowledge", but that meaning is limited to the two habitual tenses: "present simple" and "past habitual":
ami jani = I know
ami jantam = I knew, I used to know
In most other tenses it means "to find out (information)", i.e. "to come into the possession of knowledge". It often implies active enquiry to get the information, so like Hindi "pataa lagaanaa". So:
ami janchi = I am finding out
ami janbo = I shall find out
ami janlam = I found out
----------------
Now coming back to your question, you can say:
o/uni kothakar lok/manus, jenechho? (Have you found out where he is from?)
ami kal(ke)-i janlam, o/uni bangladesher lok/manus. (I learnt/found out yesterday that he is from Bangladesh.)
["lok" may be perceived to be somewhat impolite by some speakers (especially in Bangladesh). In my own speech (from West Bengal), "manus" sounds a bit odd in this usage, while "lok" sounds neutral.]
Bonus Information:
Though the above-mentioned sentences are natural, you may hear more often:
o/uni kothakar lok/manus, jante perechho?
ami kal(ke)-i jante parlam, o/uni bangladesher lok/manus.
Literally, "was/were able to find out". These sentences are agnostic about any active enquiry. Maybe you found out the information by accident, more like Hindi "pataa chalnaa".
---------------
Additional information if your level of Bengali is higher than a beginner's:
Of course, like almost any verb in most South Asian languages, there are various compound verbs with subtle semantic distinctions, that are possible with "jan-a". Two important ones are "jene ja-wa" and "jene ne-wa", the first one is strongly suggestive of finding out without asking (and possibly even without consent!) and the second one is strongly suggestive of active enquiry. Hindi possesses the direct parallels in "pataa ho/chal jaanaa" and "pataa kar/lagaa lenaa". They can be used also in habitual tenses when the "find out" meaning is required:
ami jene jai = I find out (without asking)
ami jene nii = I find out (by asking)
"jante par-a" is ambiguous in habitual tenses:
ami jante pari = I find out / I may know
ami jante partam = I used to find out / I may have known