Moving our infrastructure to AZURE

I think the aforementioned PoC is a great suggestion.  Get comfortable with the key Azure capabilities and how they would fit in with your requirements. What you have laid out sounds like a big program of work, which I am sure is doable but it won't be without its complications. I'd suggest getting some assistance if needed, things like networking, firewalls, resilience can get quite complicated, there are also options like ExpressRoute.  Getting some help to navigate these options especially if you are on a deadline, could make sense.  Also look at costings and the different ways of paying for Azure, the most preferential is usually via an Enterprise Agreement, also if you have been buying your Windows Server licences with SA, you should be able to make use of Azure Hybrid Use Benefit to save on costs. Finally, you also want to make sure you understand IaaS vs PaaS and the corresponding options in Azure like Azure Virtual Machines vs Azure Web Apps.  The main https://docs.microsoft.com/en-us/azure/ is very good.