The maps will be all black because the editor doesn’t know which textures to use when it converts from old maps to new. After loading a map through “Convert legacy map” you have to go to Map > Map textures and then select a few textures and click ok. The map will now be textured and you will see it’s shape and so on, but you will notice that any elevation differences, like rivers or higher ground in Starcraft 1 maps, will be represented by plain differences in height of normal ground. Aka, if you take an scv and walk into what is supposed to be water, the scv will just go to the bottom and up on the other side. You have to manually “fill in” the old map with SC2 cliffs/rivers etc.