How to install dependencies of specific Workspace using Lerna

I'm using Lerna with a monorepo typescript app, that has this structure:

app/
  backend/package.json
  frontend/package.json
  common/package.json
./package.json

I'm also using yarn to install dependencies.

My lerna.json is like:

{
  "packages": [
    "app/*"
  ],
  "version": "0.0.0",
  "npmClient": "yarn",
  "useWorkspaces": true
}

My root package.json is like:

"workspaces": [
    "app/*"
  ],

Each one has is own package and the root has common packages.

I need to generate the node_modules of only the backend prod package.

How can I do that?