Adding two histograms wih different x-axis

Hi, I wanted to superimpose my simulated decay spectra of Bi-207 with one from the experiment.
I saved the two histgram as a .C file and tried to superimpose them but the issue is my simulated spectra is in MeV range while the one from the experiment is in KeV.
How do i scale on the x - axis?

Use SetLimits: