no matter "numbers" or "nos", it should still read it as "numbers". "nos" is just the short form of "numbers" in writing.
Just like the word "etc" is the short form of "et cetera" which means "so on". But you will not read it as the letter "E" and "T" and "C", you will read it as the original word "et cetera".
Since that "nos" is just the short form of "numbers", therefore it should still be pronounced as number.
This is similar to "pt" as a short form of "point", but still be pronounced as Point and "Mr." is the short form of "mister" and you still be pronounced as Mister.