"So a petabyte is 1,000 terabytes, which is 1,000 megabytes.”
I am hardly a whiz at either math or computer science, but it is my understanding that one petabyte = 1000 terabytes, one terabyte = 1000 gigabytes, and 1 gigabyte = 1000 megabytes. So, gigabytes seem to have gotten skipped in the definition (unless I’m missing something, which is always a strong possibility whenever I wade into this forum).
Also, at the risk of obnoxious nitpicking, saying a petabyte is 1000 terabytes which is 1000 megabytes would mean, among other things, that 1000 terabytes = 1000 megabytes (again, unless I am missing something). While its probably obvious to a reader that that’s not what is meant, I think it helps to add in what “one” terabyte is, etc. Or you could say something like 1 petabyte is 1000 terabytes which is 100,000 (?) gigabytes which is 100,000,000 (???) megabytes. (The question marks indicating that my confidence in my math is decreasing exponentially).