Hi Melony,
Chef Mickey's is located within Disney's Contemporary Resort which is the closest hotel to the Magic Kingdom theme park.
We LOVE dining at Chef Mickey's and when visiting this restaurant you will normally be visited by Mickey Mouse, Minnie Mouse, Donald Duck, Pluto and Goofy although please bear in mind that characters are always subject to change.
You are able to travel between the Magic Kingdom & the Contemporary Resort by either taking a short walk or the monorail. Both of these journeys will take approximately 10 minutes time.
If you are looking for another character meal which is located close to the Magic Kingdom where you can usually find Mickey Mouse, perhaps you could consider
Ohana's Best Friends Breakfast with Lilo & Stitch at Disney's Polynesian Resort. The best way to get from here to the Magic Kingdom would again be to take the monorail.
Character meals are very popular so I would highly recommend that you make advanced dining reservations as soon as possible.
Wishing you a magical trip!