Using my Hungarian Village Finder, Atlas, and Gazetteer for the Kingdom of Hungary cd-rom: http://hungarianvillagefinder.com/cdrom/CD.htmlhttp://hungarianvillagefinder.com/cdrom/CD.html there are/were not too many places that began with the letters "Con" but it would not be too difficult for the following to be confused with Constantinople :-)
Conopla, Conoplja, Csonoplya were all names for the fairly large settlement called Csonopla in the old Kingdom of Hungary.Csonopla was in the old Zombor Járás, Bács-Bodrog Megye.You can see it on this map from Eötvös University, Department of Cartography: http://lazarus.elte.hu/hun/maps/1910/bacsbod.jpghttp://lazarus.elte.hu/hun/maps/1910/bacsbod.jpg
Today, it is in what was Yugoslavia but is now Serbia and called Conoplja or Conopla.Keep in mind though, that before WWI there was no Yugoslavia so it probably was Romania.People more familiar with the history of this area will be able to provide you more info with that.
HVF shows there was a Roman Catholic Church and a Jewish Synagogue in Csonopla.From the HVF program you can link to the LDS site for Bács-Bodrog Megye or click here: http://www.familysearch.org/eng/Library/fhlcatalog/supermainframeset.asp?display=http://www.familysearch.org/eng/Library/fhlcatalog/supermainframeset.asp?display= localitydetails&subject=73132&subject_disp=Hungary,_Bács-Bodrog&columns=*,180,0
If Csonopla is the place you're looking for it looks like you're in luck because the LDS has filmed the Roman Catholic Church records for Csonopla from 1826-1895.