ls */

This would list the contents of all the non-hidden subdirectories in the current directory.  Since you only seem to have subdirectories with numeric names, this will show the contents of these.

The shell globbing pattern `*` would expand  to all non-hidden names in the current directory.  Adding a `/` at the end of the pattern forces the pattern to expand to only directories (since non-directories can't have `/` in their names).

With the `zsh` shell, the following filename globbing pattern would expand to only _regular_ files in each subdirectory

    */*(.)

To do something with those names that matches, you would loop over the expansion of that glob pattern:

    for pathname in */*(.); do
        # use "$pathname" here
    done

In `bash` or `sh`, you would call a small script from `find` instead:

    find . -mindepth 2 -maxdepth 2 -type f -exec sh '
        for pathname do
            # use "$pathname" here
        done' sh {} +
    
But that's really just a fancy way of writing

    for pathname in */*; do
        [ ! -f "$pathname" ] && continue
        # use "$pathname" here
    done

except that the `find` variation would skip symbolic links to regular files and include hidden names (set the `dotglob` shell option in `bash` to include these).

Again, this would do what you wanted (look in directories with numeric names) because you appear to *only* have subdirectories with numeric names.

Assuming that there may be other subdirectories too,

    for pathname in */*; do
        [ ! -f "$pathname" ] && continue
        case $(dirname "$pathname") in
            *[!0-9]*) continue
        esac
        # use "$pathname" here
    done

or, with `bash`,

    for pathname in */*; do
        if [ ! -f "$pathname" ] ||
           [[ $(dirname "$pathname") == *[!0-9]* ]]
        then
            continue
        fi
        # use "$pathname" here
    done

These loops would loop over all the names in the subdirectories, but would skip any name not referring to a regular file (or a symbolic link to one), and would also skip any file in a subdirectory whose name contains anything that is not a digit.

With the `extglob` shell option in `bash`, you could make that a bit shorter:

    shopt -s exglob
    for pathname in +([0-9])/*
        [ ! -f "$pathname" ] && continue
        # use "$pathname" here
    done

The pattern `+([0-9)/` would expand to names of directories that only have digits in their names. This would also work in `zsh` if the `KSH_GLOB` option was set instead of `extglob`.

With GNU `find`, you could obviously pick out your numeric directories and then loop over their contents:

    find . -maxdepth 1 -type d -regex '.*/[0-9]+$' -exec sh '
        for dirpath do
            for pathname in "$dirpath"/*; do
                [ ! -f "$pathname" ] && continue
                # use "$pathname" here
            done
        done' sh +

but I don't generally suggest using regular expressions on filenames or directory names since they are mainly for matching text in text files. GNU `find` obviously supports matching pathnames with regular expressions, because GNU software tries to be as convenient as possible.