Hi Gianni,
It sounds like a bit of an overkill to buy ArcGIS just for converting a set of json files. I'm sure there are other (free) options that can do the job. You mentioned that you want the points inside the file converted to WGS1984. The content of the json you send is a polygon (area).
In case you want to use ArcGIS for it (maybe you can download a trail version), you can use some python script to convert the file. Since at this location I only have access to 10.1, the options to convert json are a bit limited. Below you'll find a Python script (using ArcGIS) that converts the json to a kmz file (WGS1984). I'm sure there must be easier ways to do this. I'll attach the kmz file so you can have a look if this type of information is what you ware looking for.
import arcpy, json
arcpy.env.overwriteOutput = True
json_file = r"D:\Xander\GeoNet\SanPietroJSON\json\SanPietro.json"
out_shp = r"D:\Xander\GeoNet\SanPietroJSON\shp\SanPietro_merc.shp"
out_shp_wgs = r"D:\Xander\GeoNet\SanPietroJSON\shp\SanPietro_wgs84.shp"
out_kmz = r"D:\Xander\GeoNet\SanPietroJSON\kmz\SanPietro.kmz"
# spatial references
sr_in = arcpy.SpatialReference(102100) # Web Mercator
sr_wgs = arcpy.SpatialReference(4326) # WGS 1984
# process json file
dct = eval(open(json_file).read())
lst = dct["results"]
dct2 = lst[0]
geom = dct2["geometry"]
rings = geom["rings"]
# create feature(s)
features = []
for feature in rings:
features.append(arcpy.Polygon(
arcpy.Array([arcpy.Point(*coords) for coords in feature])))
# create featureclass (shp)
arcpy.CopyFeatures_management(features, out_shp)
# define projection
arcpy.DefineProjection_management(out_shp, sr_in)
# project to WGS1984
arcpy.Project_management(out_shp, out_shp_wgs, sr_wgs)
# create featurelayer
arcpy.MakeFeatureLayer_management(out_shp_wgs, "WGSpoints")
# convert to KMZ
arcpy.LayerToKML_conversion("WGSpoints", out_kmz)
Kind regards, Xander