[Landscape] I don't getting any height maps

Hi everyone i want a help i trying to make a city like vancouver city and when i make a landscape its square i dont get any height maps for it is there a way to make it looks like that? or if its not with landscape what is the way? i dont getting any height maps

Which documentation for landscapes via height maps are you looking at? (link, please)

Use NASA satellite images. They are good for importing heightmaps. You just need to login to earthdata
https://urs.earthdata.nasa.gov/

Then use the GDEx(LP DAAC) option .Drag and select an area to highlight .Save as jpeg .Convert into png using any image editor tool . Hope this helps