You need a upright 12" wheel at least. Smaller wheels and saucer wheels in the long run if only having that wheel will end up hurting their backs which isnt really the best thing and you cant fix that.
It took me like 4-5 weeks to help Holly get used to her wheel.
A lot breeders wont have introduced wheels to them, some may have during play time but a lot wont have. Depending on the breeder you get mostly and what they think.
If you use my first suggestion you should crack the whole not using his wheel soon enough.