"Tiled Maps & Tilesets to Unity" is a lite, simple tool to convert a Tileset image file to a set of Textures and Materials, then use them to convert a map created in Tiled to a perfect 3D recreation. It will also automatically create the walls for you.

Most importantly: all of this can be done with a single click in Unity.

You will need the free program Tiled to create the maps: http://www.mapeditor.org/

A 'Readme' file is included in the package; it should give you all the information you need.
Make sure to read the Troubleshooting section before asking a question.

There is also a demo tutorial video posted.