I have a Novara Buzz bike that I bought at REI (in 2015?).    I'd like to replace the stem that came with the bike with a stem that's adjustable, so the handlebars can be a little higher than they are currently.  I'm not sure of the size of the handlebars and steerer tube - this information seems to be required in order to get the correct size replacement.

Can you help me determine the size, please?  I've seen listings for stems that are 25.4mm and 31.8mm (or 1 inch and 1.25 inch). (Someone had this exact question that I am trying to do so just copied and paste did this 🙂 thanks for any info!