I can tell you right away that the town you are looking for is Velikaya Mysa in Belarus, which is pretty much the translation for Wielkamysa (the latter being Polish and the former being Belorussian. It means something like "Great Cape").

It was and probably still is, pretty tiny with about 501 inhabitants in 1938, shortly before the USSR would invade Poland and include the village as part of the Belorussian SSR. And that's pretty much it in terms of what you can find about it on the fly without delving into Belorussian sources, which I am unfortunately unable to.