When I write some business emails, I usually encounter stating Week number like this.
I hope you to ship ABC goods on(?) / at(?) / in(?) week number 09.
Looking back upon my history, some colleague uses “on” with week number ##.
However I am not sure which one is suitable for being used with week number ##.
FYI) ## denotes digits like 1, 2, 3, 4, 5 and stuff.