If you buy 6 x 10 you will have to make it approx 10% smaller to fit the maximum9.1".
If you have the right software this should be no problem. Maybe someone knows free software to do so. I have software from Husqvarne and that can easily do this but it is expensive. Maybe you have software that came with your machine. Good luck.

No you can't Corinney.Not with the MC350E.The largest hoop you can use is the B hoop,5.5" x 7.9".
You can get a Giga Hoop for the 350E. But you will not be able to do large designs with it unless you use designs that have been digitised for the Giga Hoop, or you know how to split a large design. The Giga Hoop has 2 parts to it, both the size of a B hoop.
When you got your 350 E,you should have also been sold either a customiser of Digitiser Junior.
This is the software for the Janome.
If you want to reduce, or increase a design you can use your machine.It will only allow you to increase by 20% and decrease by10%. You must go into edit to do this.

Here is the link under the editing and splitting tab. Hope this helps.