Cobner, Russia and the rest say either Russia or Poland....
The town is most likely Kowno in today's Lithuania. The town of Kowno was on the territory of the Polish-Lithuanian Commonwealth that ceased to exist in 1795. Although in that year it became a Russian town, I bet that in 1842 its inhabitans could have still thought of it as "Polish".
The letter "w" can be easily mistaken for the letter "b" by those to whom the name Kowno was unfamiliar. The final "o" which in Polish is pronounced without any phonetic reduction (as it would be in English) may have easily be taken for the ending -er by an English speaker. Hence, in my view, this transformation from "Kowno" to "Cobner".