I agree, it seems that the n on your star chart stands for NGC;
A quick reference for what each NGC or IC obect is, is the NGC/IC project website:
http://www.ngcicproject.org/pubdb.htm
NGC 3293 is an open cluster in Carina
NGC 4349 is an open cluster in Crux
NGC 4103 is an open cluster in Crux
The star atlases vary greatly in the number of deep sky objects thay show. Some of them show only the bright or fairly bright objects in a constellation, while others (especially the software star charts) can plot hundreds of thousands, or even millions, of non-stellar objects.
You will see plenty of sources where NGC is shortened to N, for example,
instead of the galaxy NGC 253, someone might write N253 or N0253.
The NGC and the IC catalogs contain most of the visually obvious non-stellar objects in our sky, as they were based on the sky surveys done by the 19th and 18th century observers, notably the Herschels.
However, these people missed a good number of fairly obvious southern objects, and also they missed a lot of low surface brightness galaxies and very extended nebulae which are difficult to see - but nonetheless still visible - for modern deep sky observers.
So then one has to access objects in a lot of more exotic catalogs such as UGC (for galaxies), and RCW (for nebulae) and ESO (for some moderately bright southern galaxies missing in the NGC and IC catalogs)
We have a member called glenc who is a master of the history of these catalogs, while I am more specialized in the obscure catalogs of galaxies.
You need good tools that show adequate stars for finding the objects you wish to see, and which have enough deep sky objects plotted.
Others are more qualified than me to recommend sky plotting tools for people who are at the beginning to intermediate amateur level.