how to populate contact counts from all contacts in landing page

There's no specific data view that serves this purpose, but if you have Mobile Connect enabled in your account you can extract the data this way:

1. Create a filtered list in Mobile Connect with a single condition Contact Key is not null
2. Create a data extension with a single column: SubscriberKey
3. Query the filtered list and send the results to your data extensions: Select SubscriberKey from [YourMobileConnect list name from step 1]

(This process is a reverse-engineered from an article that shows how to remove unwanted customers: Permanently remove Contacts or Subscribers and associated data from Contact Builder)