This is a paid asset, but now you can download Post Apocalyptic World Pack Free.
Detail this asset from Unity Store: Original Link
Post Apocalyptic World Pack v1.1 (Latest version)
“If possible, please buy the package to support the developer”
The Post Apocalyptic World Pack has over 100 uniquely crafted assets allowing you to create vast open worlds or detailed linear levels. Choose from a wealth of uniquely crafted meshes each with materials, textures, lods and collision set up for optimal performance. Designed in a modular fashion, simply drag and drop to create the level of your choosing.
30 +Buildings with detailed building for close up detailed and lower for more distance buildings including shop signs and attachments.
15 foliage assets including trees, bushes plants and grass with numerous variations allowing you to create the over grow levels with an organic feel.
6 Organic assets such as rocks & grounds
13 Roads assets with damage, bridges, turns and hill variants
64 Props and structures ranging from sand bags and barb wire, vehicles, to dumpsters and rubbish adding the finishing details to this post apocalyptic living breathing world.
An example level showing you a glimpse of what you can create has been included with lighting and post processing effects giving you the game ready art you see in the screen shots.