Extract part of a filename shell script

In bash I would like to extract part of many filenames and save that output to another file.

The files are formatted as coffee_{SOME NUMBERS I WANT}.freqdist.

#!/bin/sh
for f in $(find . -name 'coffee*.freqdist)

That code will find all the coffee_{SOME NUMBERS I WANT}.freqdist file. Now, how do I make an array containing just {SOME NUMBERS I WANT} and write that to file?

I know that to write to file one would end the line with the following.

  > log.txt

I'm missing the middle part though of how to filter the list of filenames.