Buying a new server, need help

Hey all,

It has been a while since I have posted on the forums. I am currently taking my capstone class for Network Admin degree. The project myself and two other team members are working on is upgrading a local non-profit from a windows server 2003. They currently have 2 Dell Poweredge 1950s and a Poweredge R510, which I am fairly confident is a NAS device. My group and I are hoping to make the jump to server 2016 rather than 2012 so that it can last another 15 to 20 years possibly like the current setup has.

I was wonder if there is a way to calculate the performance needed from certain windows server services. This company uses Active Directory, DHCP, WSUS, and a couple of others I can't remember off the top of my head. Anyone who can chime in and give some direction or resources is appreciated. Might even get a visit from @wendell if I'm lucky. If you have any questions let me know and I will answer the best I can.