Classic 3D is a resource pack that turns the default models into more complex and detailed blocks, while still looking like Minecraft.

HOW TO DOWNLOAD!

To download it all you have to do is head to the link above after doing so, press win + r in your keyboard a pop up will appear search for the following %appdata% and then click ok or enter.
After all of this you should be greeted with a folder you are going to find .minecraft if you are there that means you are still following along side with me, then head to resourcepacks and drag your resourcepacks into the folder and there you go just make sure to reload Minecraft and that is it!