1. Copy the Documents folder as it contains game saves (some are also in Documents-> My Games, and some are also online)
2. copy the entire "Steamapps" folder as that contains all your games (or leave on the same drive if that's better... as long as you don't delete that folder)
3. If you use MODS write down the name of all the mods so you can clean install those later
4. Install W10
5. Install Steam (default, c-drive) and login
6. If your game folder needs to be on a different drive such as E-drive then go into Steam settings and create that library folder (i.e. "E:\Steam2")
7. MOVE the Steamapps folder into the new Steam folder
8. Restart Steam (or just Reboot)
9. Start a game to test (one without mods), but VERIFY the game local content first
10. Copy over SAVES as needed
11. For SKYRIM you probably need to:
a) verify game content
b) install Nexusmods (if installed before)
c) reinstall all the mods
If you're good with mods you can copy over the downloaded RAR files, possibly reconnect to a saved MOD FOLDER but that's beyond the scope of this article and not how I do it.
I also suggest keeping a BACKUP of any game you intend to mod so you can restore the original version if things get messed up.
Other:
SKYRIM benefits from an SSD much more than most games as it has lots of load points. Any time you jump map locations or enter a building/dungeon you might decrease the wait by 3X or so. Not much difference between a slower and faster SSD, but a lot of difference versus any HDD.