I'm pretty new to Blender so I don't know if this is my stupidity or something else. I realized that my icon for meshes changed and I can't access them. I don't know if its something I did because every model I try to work with has the same problem. Sorry if this is a really simple problem but I really need to know.
Perhaps, you are looking at the material data-blocks (i.e. the first image you have put it up here) instead of the object data-blocks.
Look out for Blender File as a Display Mode on your Outliner. You should have all the data displayed that is present on your current Scene.