If You created one new project under Feature Folder and also add Serialization.config file under this project app_config folder .
Then you will see In this config file under configuration node there is mentioned .... extends="Helix.Feature" >.
You can find the configuration name="Helix.Feature" is inside Unicorn.Helix.config file .
If you download the habitat solutions from Github then you can find this file inside Sitecore.Foundation.Serialization --> app_config project folder .
Look the line in this config file under Helix.Base configuration node
<targetDataStore physicalRootPath="$(sourceFolder)\$(layer)\$(module)\serialization" useDataCache="false" singleInstance="true" />
So, this line will find your serialization folder from your solutions , Generally we create on new zDeveloper.config file under app_config --> Include --> Project folder
and mentioned the local solutions path in there like below :
<sc.variable name="sourceFolder" value="Your Habitat Solution Folder Path \ src" />