Update part3c.md

In the .env file - MONGODB_URL="mon...".
In the models/note.js file and further - const url = process.env.MONGODB_URI. Since MONGODB_URL was used only at the beginning, and MONGODB_URI is also in the repository, I replaced MONGODB_URL with MONGODB_URI

Author: lemon1964

src/content/3/en/part3c.md

@@ -392,7 +392,7 @@ const Note = mongoose.model('Note', noteSchema)
 To avoid authentication issues with the password variable in index.js, we need to create a .env file by running npm install dotenv in the command line. Then, let's create the .env file in the root of your directory. In that file, you should place your URI:
 
 ```
-MONGODB_URL="mongodb+srv://fullstack:[email protected]/?retryWrites=true&w=majority&appName=db"
+MONGODB_URI="mongodb+srv://fullstack:[email protected]/?retryWrites=true&w=majority&appName=db"
 ```
 Don't forget to replace the string with your details. 
 Once the .env file is ready, remember to add it to your .gitignore file to prevent pushing the password to Git:
@@ -404,7 +404,7 @@ Once the .env file is ready, remember to add it to your .gitignore file to preve
 Then, in your index.js file, make the necessary changes with the following line so that your code can access the URL in your .env file:
 
 ```
-const url = process.env.MONGODB_URL;
+const url = process.env.MONGODB_URI;
 
 ```