Yes, I think that is the right number for a 32 bit float. Either way, it's going to be way way larger than any distance you plan to measure with Arduino. 3*10^38 meters would be on the order of 36000000000000000000000 light years. That's about 400 billion times the diameter of the known universe.

I think you'll be alright with whatever number you need to use.

But you could always have more precision, less error, and faster calculations if you used long integers and used fixed point math. If you need meters to 2 decimals, then use millimeters instead. Need millimeters to 2 decimals, use micrometers instead. You can always scale it so you're only working with integers.