Run this command ng generate module app-routing --flat --module=app to create app-routing.module.ts file then add the code const routes: Routes = []; like this
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import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { RouterModule, Routes } from '@angular/router';
const routes: Routes = [];
@NgModule({
declarations: [],
imports: [
CommonModule, RouterModule.forRoot(routes)
],
exports: [RouterModule]
})
export class AppRoutingModule { }