Here's the definition of sudoku in Wikipedia:
How should one read 9×9の or 3×3の out loud?
I think you're asking this because in English, we distinguish times from by:
But I think in Japanese, it's just かける in both cases:
You can see that both uses are listed on Wikipedia's article for
× in the same section (titled 積), and in that section it says that the symbol is usually pronounced かける.
This ALC example also uses かける to correspond to English by, although this example has units:
Also about the photo size, would you like it four by six inches or three by five inches?
I also found some videos online where
× was used to express dimensions, and they pronounced it かける in each case. For example, this video and this video say 2×2 and 3×3 as にかけるに and さんかけるさん. (They're both Minecraft videos.)
So I think you can just say "number かける number".