i want to save my project from build

The modding community has some tools to manipulate built Unity games. Those toosl are completely unrelated to the official Unity3D site and are in no way shape or form supported or licensed by Unity3D.

I’m sorry you’ve had this issue. Please consider using proper industrial-grade enterprise-qualified source control in order to guard and protect your hard-earned work.

Personally I use git (completely outside of Unity) because it is free and there are tons of tutorials out there to help you set it up as well as free places to host your repo (BitBucket, Github, Gitlab, etc.).

You can also push git repositories to other drives: thumb drives, USB drives, network drives, etc., effectively putting a complete copy of the repository there.

As far as configuring Unity to play nice with git, keep this in mind:

I usually make a separate repository for each game, but I have some repositories with a bunch of smaller test games.

Here is how I use git in one of my games, Jetpack Kurt:

Using fine-grained source control as you work to refine your engineering:

Share/Sharing source code between projects:

Setting up an appropriate .gitignore file for Unity3D:

Generally setting Unity up (includes above .gitignore concepts):

It is only simple economics that you must expend as much effort into backing it up as you feel the work is worth in the first place. Digital storage is so unbelievably cheap today that you can buy gigabytes of flash drive storage for about the price of a cup of coffee. It’s simply ridiculous not to back up.

If you plan on joining the software industry, you will be required and expected to know how to use source control.

“Use source control or you will be really sad sooner or later.” - StarManta on the Unity3D forum boards