Answer:
Yes obviously... but double prefixes are officially prohibited by SI. A megagigabyte would actually be called a petabyte.
1000 kilobytes (kB) = 1 megabyte (MB)
1000 megabytes (MB) = 1 gigabyte (GB)
1000 gigabytes (GB) = 1 terabyte (TB)
1000 terabytes (TB) = 1 petabyte (PB)