WRF: EPSG code or spatial reference for Lambert conformal, Mercator and polar stereographic projections
Spatial reference systems are coordinate systems that can be geographical coordinate systems defined on a model ellipsoid or projection coordinate systems.

A projection coordinate system is defined by four groups of parameters: 


model ellipsoid, 
projection type
projection parameters
measurement unit


EPSG codes refer to complete spatial reference systems or model ellipsoids.

You are saying that you want an EPSG code for projection coordinate systems that  use WGS84 as model ellipsoids and Mercator, Lambert conformal conical, and stereographic projections. These projections require additional parameters such as the central meridian and origin latitude. Choice of parameters depends on your region of interest.

You could start with EPSG:4326 which is a geographical coordinate system with degrees as units.

Next, since your region of interest seems to be in the south of Brazil, consider EPSG:32722 that stays for Universal Transverse Mercator zone 22S and uses the WGS84 ellipsoid.

For a Lambert Conformal Conic projection consider ESRI:102015 that stays for South America Lambert Conformal Conic. This spatial reference uses a model ellipsoid that is different from WGS84, so this might be a problem for you. The standard parallel numbers for this projection are 5S and 42S meaning that the distortion would be greater for regions that lie away from these latitude, i.e. the Northern hemisphere or the Antarctic regions.

Finally for a Stereographic Polar you might consider EPSG:3031. An Antarctic Polar Stereographic projection coordinate system that uses WGS84 as a model ellipsoid.