A. Wow, that's a lot of slides! This project could turn into a lifetime undertaking! Homebound scanners, even those with slide feeders, can make this work tedious. Unless you just like doing this, I suggest you consider having the slides scanned commercially.
However, Nikon and Konica Minolta do have scanners available that will work with slides. Before we get into that, let's consider some specifications. For scanning slides, I recommend at least 2600 dpi (dots per inch) optical resolution.
When shopping, ignore digital resolution. This uses interpolation to create pixels through digital enhancement. Interpolation is another word for "guesswork." It probably will degrade your image. So, make your decision based on optical resolution.
Buy a scanner with at least 24-bit color depth. That is true color. Some scanners offer higher color depth. But you are unlikely to notice the difference.