Welcome to the site !!
Yes for the rear , you can use a 450R wheel if you want a 19" instead of the 18" X wheel (or a CR250R *2 stroke* from 02-07) , just bolt it on and go , you can use from 2002-2012 from the 450R without issues , the rear hub offset was changed in 2013 so the wheel won't align properly , for the front you will need the axle and spacers for the R wheel , 1995-2015 should bolt right on as long as you use the axle parts as mentioned , (and take off or tie up your speedo cable if it still exists) , or you can use from 2005-2016 450X for front/rear , and/or 2004-2016 250X front wheel , but not the rear as the 250X has a 1.85 rear rim width like the CRF 250R , so its a bit too narrow for the 450
The only other swap/change you will have to make is the chain/sprockets , as i believe the SM is like a 13-14/34 or something correct ?? , you will want between a 13/48 - 13/52 depending on what type of riding your doing , if its tight single track the 13/52 should be good , its what i run on mine , if your riding desert , then go with the 13/48 or anywhere in between , or depending on the speed and your skill level , 14/47 if you like doing 100+ thru the desert ...the gearing is subjective to your specific needs and how you like the bike to work .................. Hope that helped .........