Could not load type Microsoft.AspNetCore.Internal.EndpointRoutingApplicationBuilderExtensions from assembly Microsoft.AspNetCore.Routing Ver=3.1.7.0

I am upgrading my dotnet core 2.2 app to 3.1. I have multiple services and one base library all initially developed in 2.2 AspDotNetCore. My plan is:

1. First covert my base library to Dotnet standard 2.1. Which I am able to do successfully with few reference changes.
2. Now I am referencing this base 2.1 dotnet standard library in other AspDotnet core app which I am upgrading from 2.2 dotnet core to 3.1 dotnet core. Here I am getting error as follows.

Could not load type 'Microsoft.AspNetCore.Internal.EndpointRoutingApplicationBuilderExtensions' from assembly 'Microsoft.AspNetCore.Routing, Version=3.1.7.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'

The at which this error occurs is at UseMvcCoreServices which is my custom extension mention:

 public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IHttpContextAccessor ca, IHostApplicationLifetime applicationLifetime)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app
            .UseMvcCoreServices(Configuration, Logger, env)
            .UseElasticClient(Configuration, Logger);

I followed lots of link as: [https://medium.com/@alexandre.malavasi/migration-from-asp-net-core-2-2-to-3-1-real-project-ca382ea7eef7] and [https://docs.microsoft.com/en-us/aspnet/core/migration/22-to-30?view=aspnetcore-3.1&tabs=visual-studio]

But yet no luck. Can someone help me. It's really critical for me.