MATLAB: Convert to Mercator projection

Mapping Toolboxmapping; mercator;

Attached I have a map… is there an easy way to make this projection Mercator? I am still a novice when it comes to mapping so any help would be greatly appreciated.
Oh and while we're at it, I must plot point on this map… but this code: "plotm(41,-103,'r','MarkerSize',20)" only makes an extremely small dot… despite adjusting MarkerSize..
Again, any assistance on both problems would be greatly appreciated!
figure
worldmap([30 50],[-110 -70]);
geoshow('Shapefiles/cb_2013_us_county_5m.shp', 'FaceColor', [.5 .5 1]);

Best Answer

Converting projections after plotting doesn't usually work. To initialize a mercator map with those lat/lon limits, try this:
axesm('mercator','maplatlimit',[30 50],'maplonlimit',[-110 -70])
geoshow('usastatehi.shp')
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