If your going to keep him his requirements should be fairly simple. A hamster cage with bars close enough together so he cant squeeze himself through, with a water bottle, an exercise wheel and a nesting box. Feed him on rodent food (don't know if they do any specifically for mice) and give hm lots of nuts, fresh veggies and little scaps of whatever your eating as treats
Put wood shavings in the bottom of his cage and use a shredded tissue type bedding for his nesting box. Stay away from the cotton wool stuff they can choke on it.
Don't know if hat helped you at all but there ya go
