Whether it's 32 or 64 should be labeled on the disc.
If it's not, you can try running setup.exe from a 32-bit Windows installation. If it launches, it's 32. If not, it's 64.
N3051M is correct in that Ultimate is the only one that contains both versions, but that's only in retail. OEM contains only the one you ordered, you need to get the other one from Microsoft for a fee (no idea why they do that).