In EF6 we usually able to use this way to configure the Entity.
public class AccountMap : EntityTypeConfiguration
{
public AccountMap()
In ef core we have to impelement IEntityTypeConfiguration instead of EntityTypeConfiguration in this case we have full access to DbContext modelBuilder and we can use fluent api but in ef core this api is a litle bit diferent from previous versions. you can find more details on ef core model configuration on
https://www.learnentityframeworkcore.com/configuration/fluent-api