You'll need two things.
filesize.bat
@echo off
echo %~z1
And then what you're actually trying to size up.
Copy a file only if it's larger than zero / copy only a non-zero file
for /f %i in ('filesize filesize.bat') do set z=%i
if %z% gtr 0 ( copy filesize.bat noodles.bat )
I found this thread and it was almost what I needed, I tried a bunch of different things - this was mildly frustrating because robocopy looked to have /min:1 but got ALL bunged up because I wanted to rename the file in transit which made me have to use @#$!! batch script.