You should be able to continue to call campaigns endpoint and you can confirm with a Twurl call like this:
twurl -H ads-api.twitter.com ‘/1/accounts/:account_id/campaigns?sort_by=updated_at-desc’
For many of the endpoints (all besides those called out specifically in migration guide) it’s simply a matter of changing the 0 to a 1.
The entity_id is simply a catch all and not a separate type of ID being returned (to call for Campaign stats simply pass the campaign_id as the entity_id)
Good luck with your migration!
John