How to organize IT department with such input data --->?

Question

ITIL

Colleagues!
There are 3 buildings. Two are nearby (connected by FOCL), one is at a different address (connected via VPN).
30 units of network equipment (7 switches, access points, routers)
200 workstations.
ACS, equipment control systems (3-4), pressure / temperature monitoring systems (only computer parts).
2 servers (main and replica), they run virtual machines with SQL, DC, Document Management System, 1C, file storage.
The IT department is also working on finalizing and administering the document management system and developing an internal Delphi program - an electronic journal system.
Procurement, budget development, selection of suppliers, coordination of purchases with the parent company also hang on IT.
The development of procedural documents also hangs on IT, and !! validation of computerized systems (i.e. documenting that they work correctly).
Question! How many people are needed for such an IT department and how best to organize its structure?

Answer 1

Octopus admin with a split personality and diplomas in management-economics-programming-administration + liability.
This is hell. Split into areas of responsibility and 1-3 for each. Well, it's xs, maybe it's fundamentally not true.

Answer 2

Procurement, budget development, selection of suppliers, coordination of purchases with the parent company also hang on IT.

In my opinion, you made a mistake, this should not apply to IT.