I have the same info need in spite of the fact I have been in IT for decades as a developer and system admin I have never been exposed to the day to day network

I have the same info need in spite of the fact I have been in IT for decades as a developer and system admin I have never been exposed to the day to day network needs of the enterprise. I am unsure of even the questions to ask as I have unknown unknowns. I need case studies of business with sizes like 100,500,1000,1000+ endpoints with their corresponding application and security needs.