I was wondering if someone could help me with a problem of units!

I'm currently deriving probability equations for neutrino oscillations and I'm stuck with units!

I have: [(mass)^2 * time]/[4*energy] and I want to write it as [1.27 * (mass)^2 * distance]/[Energy] with distance in metres, energy in MeV and the mass in eV^2. I get that I can use the relativist approximation to get from time to distance (taking c and hbar to be 1).

I'm just wondering how you get the 1.27 that allows you to use this conversion? I assume it is [1eV^2 * 1 metre in MeV * (1/MeV)] but I don't know what 1 metre is in MeV. Can someone explain to how determine it?

Also, if anyone could explain how to get seconds in inverse MeV that would be great!

Thanks a lot, Sam