There was no 400 EX or X produced in 2010 or 11 - production went from a 2008 400EX to a 2009 400X skip 10 and 11 then continue 12 and up 400X and then discontinue all sport versions in 2015 - gone is the 400X and the 450R, all replaced with 4-wheel drive or automatic transmission models
The part number for the sub-frame you need is 50200-HN1-A70ZA - about $570 from Honda - that's why I carry full coverage insurance on my machines