Hi suzuiscool 😁 - welcome to the forums.
Your downloaded custom maps should be in:
C:\Users\[USER LOGIN NAME]\AppData\Roaming\Red Alert 3\Maps\MAPNAME - obviously, if you have no problems running them, they should be there.
When you create a map using WB, this is where it should be saved too.
Find your maps folder by clicking on Computer on the desktop, then in the location bar at the top, R Click and select "Edit Address"
Copy the following and paste it into the location bar:
%userprofile%\AppData\Roaming\Red Alert 3\Maps
You should be able to see the maps folder there. Double click to open it and ensure that your newly created map is also there.
If not, You can either copy the new map folder there manually, or open it once more with WB and use the Save As option to change the save location.
HTH