You're missing a configuration file for some reason. Try the following.
Close all files and folders in Visual Studio Code, then close it entirely.
Create a new folder in your project directory called
.vscode. Windows Explorer won't let you do this, so do it from a terminal:
Go in to this folder and create a new file called
settings.json. The contents of this file should be as follows:
Afterwards, reopen the entire folder, and everything should start working.
If this doesn't work for some reason, you will probably need to create a new project entirely. Create a new project with "SFDX: Create New Project" and follow the prompts. The newly created project should have the Visual Studio Code configuration files you need. Afterwards, you may need to authorize your orgs again, or you can try copying the .sfdx folder from the old project folder.