Super easy to put a 1 1/8th stem on a 1 inch threadless fork. Any local bike shop would probably have a few shims floating around.

If you are unsure of the length, just get the longest because almost any length you get, you're going to want to chop it down. If you really want to not waste, you can measure the headtube + how high you want to put your stem on and that would be how long you would want the length of your forktube so you'd get the fork with the fork tube length that is at least that long. You have a pretty tall bike so i would probably think you'd get the 200 or 230.