To simplify managing Apple devices and apps, Apple has combined the capabilities of the Device Enrollment Program (DEP) and Volume Purchase Program (VPP) to a single portal now known as Apple Business Manager (ABM). Organizations can now upgrade their accounts from DEP (https://deploy.apple.com) and VPP (https://vpp.itunes.apple.com) to the new portal (https://business.apple.com). In case you are an educational institution, you can make use of a similar portal known as the Apple School Manager (https://school.apple.com) which gives educational instituations the power to manage their students and their devices.
Follow the steps given below to upgrade to ABM/ASM:
Once you upgrade to the new portal, all your managed devices and apps will be available in ABM. You can continue managing these devices and apps using Mobile Device Manager Plus, without changing the tokens till it expires. After which, you will have to regenerate the tokens from the ABM portal.
After migration, all your organization's accounts will be available in the ABM portal. You will have to associate locations and roles to these accounts. If the account was already an admin in either DEP or VPP, these roles will automatically be assigned to them. Additionally, the Device Manager role must be assigned to any other account managing the devices and Content Manager role to the accounts responsible for managing the your organization's apps.
The server tokens for managing apps in the ABM portal are created based on different locations instead of users. This means that any apps added to that location can be managed by all the technicians responsible for that location.