Should I upgrade first, and then move my Windows files, or vice versa? (Currently on Linux Mint 20.1

Linux OS is on an 1.5 TB NvME, and Windows is on a 1 TB SSD that is over 3 years old...

I'm trying to remove as many data files and equivalent program files, (Ex: Windows version of VLC for the Linux version of VLC,) and so on. With a little work, I hope to whittle my SSD down to aviation related stuff and flight simulation.

So, the question is, should I upgrade first to LM 20.2, and then bring over my data and program files, or vice versa?

Thanks.