To answer your questions:
- mklink uses the convention
link
target
. So when the computer attempts to write to C:\Users\Pictures, it is actually writing to D:\Pictures. - Again, the same thing applies. The computer will write to the link D:\appdata
- Yes, you will need to delete the folders first in order to create the link.
Here is an article that walks through something very close to what you want.
However, I do want remind you that it is perfectly safe to leave all this on your SSD. Your SSD will not fail anytime soon, even with lots of writes. Your SSD will last longer than you will want to keep your computer (and most likely the next several computers). So if you have the space on your SSD, there really is no need to move the data.