Problem in C# code "does not contain a definition of UseSqlServer and could not find an available extension method" how to solve it?

Question

ASP.NET

What needs to be connected is not clear

public class AppDBContent : DbContext
    {
        public AppDBContent(DbContextOptions<AppDBContent> options) : base(options)
        {

        }
        public Microsoft.EntityFrameworkCore.DbSet<Realty> Realty { get; set; }
        public Microsoft.EntityFrameworkCore.DbSet<Category> Category { get; set; }
    }

public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<AppDBContent>(options => options.UseSqlServer(_confSting.GetConnectionString("DefaultConnection")));
            services.AddTransient<IAllRealty, MockRealty>();
            services.AddTransient<IRealtyCategory, MockCategory>();
            services.AddControllersWithViews();
            services.AddMvc();
        }

Answer 1

Open the NuGet Package Manager. Remove all existing packages related to Entity Framework and SQL.
Then install only one Microsoft.EntityFraneworkCore.SqlServer package.

Answer 2

Apparently Microsoft.EntityFrameworkCore.SqlServer was not added