Error when attempting to import .dem terrain into SU 2022

Attempting to import a .dem file and keep getting this error.
“DEM Errors: File format not supported:”

Have tried changing formats to .ddf and renaming the file but nothing seems to work.


I am not very good at this, but perhaps the file could be opened/imported into QGIS and exported from there as a DXF if do direct importer can be found.