The Merriam-Webster Dictionary also lists both “cannons” and “cannon” as the plural forms of the noun “cannon.” (I do not personally know whether the construct such as “32 cannon” is correct in the modern English.)

Is cannon a countable noun?

"Cannon" as an uncountable noun - English Language & Usage Stack Exchange.

What is the difference between cannon and Canon?

Canon is a noun that most commonly refers to an accepted principle or rule that is followed or an authoritative list of books or texts. ... Cannon is, on the other hand, is a noun that refers to a giant gun that is usually, though not always, mounted on wheels. Also, the plural form of cannon is cannon.