In the project window (where all your assets and files are) click on one of these images and change the texture type to “sprite (2d and ui)”. That should tell unity to treat alpha as transparency. If that doesn’t work or the texture type is already set to sprite, try playing around with the alpha settings in the “advanced” tab under texture type. also if you don’t want to change these settings on every image individually, you can ctrl+click on every image, then modify them. this way you’ll be editing the settings of all of the selected images at once