You need to take into account the equations for the average speed and kinetic energy of gases.
Kinetic energy, KE = [1/2] m * v^2
Average speed, v = √[3RT/m] => v^2 = 3RT / m
=> KE = [1/2]m * 3RT/m = [3/2] RT
R = 8,314 J/mol*K
T = 254 K
=> KE = [3/2]*(8,314J/mol*K)*(254K) = 3167.6 J/mol
Answer: 3167.6 J/mol
