First, please don’t post images of code, templates, or error messages. When you want to post that type of information, copy/paste the text into the body of your post, between lines of three backtick - ` characters. This means you’ll have a line of ```, then the code (or template, etc), then another line of ```.
Is cart in your INSTALLED_APPS setting?
What are the contents of your context_processors.py file in the cart directory?