Perhaps this question makes no sense, as I have no real knowledge about relativity (it is something I intend to school myself on eventually) but I recall that time and space are the same thing. If so then presumably you can take a magnitude of a vector and consequently answer this question.
Space and time aren’t the same thing although they are deeply connected. So there are no meters in a second other than as a unit of speed - distance over time.
Light travels 1/299792458 metres in a second.
I admit this is a flat-out WAG but couldn’t the speed of light expressed in meters per second be one way to interpret the question?
1 second = 3 x 10 ^8 meters per second or ©
All EM waves travel at this speed in a vacuum.
I’m way out of my element but I think this might be the right track. Speed seems to be a ratio of time to distance.
At C, time stops. Light travels at C. Light goes 1/299792458 m/s. At C there’s 1/299792458 m/s.
What about the end of that ratio though? x/1 as x units of time to 1 unit of space?
Wow, I completely botched that. It should be the reciprocal, i.e. 299792458 m.
Not that speed. 
It’s 299,792,458 m/s. Not 1/299,729,458, which would be the inverse.
Light travels 299792458 meters in a second. Why the 1/ in front of it?
eta: nevermind, ninja’d
Of course.
It should also be remembered that it travels at this speed based on the definitions of the second and meter, which are sort of arbitrary.
Technically, isn’t the answer “all of them”?
That’s why we in physics like to normalize units so that c = 1. 