How to extract geojson from ArcGIS?

Question

JavaScript

There is a map
ammangis.jo/portal/apps/webappviewer/index.html?id...

We need to extract it in geojson format (or any other format that can be converted later to geojson) so that we can recreate the same map on Leaflet, for example here
geojson.io/#map=2/20.0/0.0

I looked at the Network tab in the browser and found something similar to geojson here
www.ammancitygis.gov.jo/arcgis/rest/services/en_am...

I somehow managed to convert it to geojson, but the problem is that the coordinates don't make any sense, for example:
[3999171.0540286717,3762436.0401037736
]
3999171.0540286717 -> 39.991710540286717
3762436.0401037736 -> 37.624360401037736

then I get the coordinates of Turkey, not Oman, as it should be. I do not know how to decipher this abracadabra?

Answer 1

The coordinates seem to be in the WebMercator projection (3785).

Answer 2

the answer lies here:

"spatialReference":{"wkid":102100,"latestWkid":3857}