How many hours is 500 megabytes?

Hours are units of time. Bytes are units of data. You cannot convert between the two without some other relationship. You could, for example specify a data transmission rate, which could then be used to calculate how many hours would be required to transmit 500 megabytes or you could specify a rate at which data is written by a device to calculate how many hours it would take to write 500 megabytes.

The question is really equivalent to something like "How many hours is a gallon". The dimensions are not equivalent, so you cannot convert from one to another like you could with quarts & gallons or with minutes & hours.