Counter add-on
I'm pretty sure this is it: https://leomoon.com/downloads/plugins/leomoon-textcounter/
You could also go under Output property and under Metadata turn on frames and turn up the text size so it's clear on screen.
Hi Cletus, just use the meta data like phoenix4690 mentioned.
That way you don't need to make sure the script is running (plus I don't think the text counter works in 2.8x)
Make sure you check "Burn Into Image" and increase the font size to something readable. (it's pretty small for large renders)