https://www.amazon.co.uk/Accidental-SysAdmin-Handbook-Primer-Professionals/dp/1484218167
​
This is a great resource for moving into a more traditional sys admin type role. Takes you through a very broad overview of all of the common, traditional tech used in small to medium (and large) organisations.
​
Aside from this, learn which OS they use for their servers. You'll probably want to pick up some basic Linux terminal/Powershell knowledge and also learn some basic networking skills.
I know this isn't much help, but there are 2 books I am reading off and on that might can help in the long run:
And Network Warrior
I hope you get it all figured out!