Re: I worked with CP/M in the 1970s.
If you do a clean upgrade ther is no problem in restoring documents from whatever source.
There is no way that I am aware of to recover programs from back-up.
Well,I have never been able to do it.
There are software programs designed to do it and I have tried them with dismal results. You need to do a fresh install of each program from the original disk or from a saved download.
All that is not so hard if you still have access to your program installation stuff.
The hard part is getting the old O/S cleaned off.
I have done that so it has to be doable by almost anybody. I just followed written step by step procedure and it worked the first time.