click on the button as shown below to open launch.json-

Give your correct file name here, where your server is starting. In my case it is app.js
"version": "0.2.0",
"configurations": [
{
"type": "node",
"runtimeVersion": "10.21.0",
"request": "launch",
"name": "Launch Program",
"program": "${workspaceFolder}/app.js"
}
]
runtimeVersion is optional, its required if you want to run it on a specific node version.And that node version should be installed on your system.