Add a Mapbox Studio style as a basemap in ArcGIS Online
Maps styled with the Mapbox Studio style editor can be added as basemaps in ArcGIS Online. Any of the preset basemaps or a custom style can be added as the primary tile layer for an ArcGIS Online project.
In ArcGIS Online, start by clicking on Add > Add Layer from Web.
Choose A Tile Layer from the dropdown.
In Mapbox Studio, go to the Style page of the map to add and click on Share & use.
Under Use style in other apps click on ArcGIS and copy the URL by clicking on the clipboard icon.