Code:

for dir in Folder*
## The shell expands Folder* to a list
## of all files and directories beginning with "Folder"
##
## "for" assigns each member of the list in turn to the variable $dir
## and executes the code between "do" and "done" using that value
do
  printf "%s" "$dir" ## print the name of the directory with no newline
  (
    cd "$dir"  ## Change the working directory to the one in $dir
    ## That should have included a test that the cd was successful:
    ## cd "$dir" ||
    ## continue ## go to the next iteration of the loop if not successful

    ## Place all the [non-hidden] files into the positional parameters
    set -- *

    if [ -f "$1" ] ## check that there actually is a file
    then
      printf "\t" ## print a TAB character

      ## Store all the filenames, with commas, in $list
      list=$( printf "%s, " "$@" )

      ## Print list of filenames without newlines
      ## and without the trailing comma
      printf "%s" "${list%, }"
    fi
   )
  echo ## print a newline
done