Show the variable how? There's not a console, there's not a way to simply display a string or character. Scratch revolves around programming sprites to do things
Tick the checkbox next to the variable in the block palette. That creates a variable watcher on the stage. You can also right-click the watcher to change it to a large readout, displaying the variable contents within a minimal frame.
Also if you get Scratch Addons (https://scratchaddons.com/) and enable the Debugger addon it adds a console and blocks to log to it.
Something as simple as this should not require add-ons. This isnt js and `leftPad` you know
Why would kids need a full debugger with console? That's far from "simple".