Help please, please help

[Dexterr Jay]

my main project urls.py file  has

urlpatterns = [

 path('mainapp/', include('mainapp.urls', namespace='mainap)),

]

and my app urls.py has the following path

path('', views.item_list, name='item_list'),

 

my allowed hosts in settings is

ALLOWED_HOSTS = ['.herokuapp.com']

i have already deployed the app in heroku, and but i'm getting a 404 page not found error when i open the app in my browser

How do I set my Allowed Hosts to  point  to https://mydomain.herokuapp/mainapp?