Export data to ASC (grid) file
Exports surfaces to ASC (grid) file (Esri ASCII raster format—ArcMap | Documentation).
Click File.
Click Create WebGL file.
This opens a new window.
File name: allows to choose the name and the path where you want to save the file.
Cell size: the size of the grid.
No data value: in case the Z is missing, this is the value that is entered.
Surface to export: select the surface to export from the list of available surface subprojects.
Click Next to define the subprojects to export and complete the export process.