Here is an example of the tag on a honda lawnmower.

On a machine that is made by Honda, you typically will only need the machine model number and you can look up all the parts on it.  If the machine is made by somebody else and has a Honda engine, you will need the Engine model number to look up engine parts.

The number will not be on a sticker.  The number will be stamped into the block and there will be a set of letters and numbers.an example of a Honda model number is

Gcv160a A2A and serial would be GJaea-10000221