If your organization has been using ArcGIS Desktop and has been paying the annual software maintenance fees, you will get an equal number of levels of ArcGIS Pro licenses. So, if you have 2 licenses for ArcGIS Desktop Advanced, 4 licenses for ArcGIS Desktop Standard, and 10 Licenses for ArcGIS Desktop Basic, you will have the same number and level of ArcGIS Pro licenses, which you can assign to users.
For completely new users, the number of licenses and levels will be dependent on what you purchase from Esri or one of their authorized business partners. Esri does offer discounts for multiple licenses as well as for non-profit and educational institutions.
ArcGIS Pro has three license levels, namely, Basic, Standard, and Advanced. The license level you have or purchase will determine the functionality of the software. Basic will have...