I think he means he wants to force the script to overwrite the folder if it exists, however, that would (probably) delete all its contents. Something like this should work:
If the directory exists it will cd into it. Otherwise it creates it. This also checks for a file with the same name as the directory you are attempting to create and exits with an error code if it finds one.
for [ i in `seq 2 9` ]; do
if [ -d hello$i ]; then
#if file with name exists
if [ -f hello$i ]; then
echo "error $0: there is already a file with that name"
# exit 1 is error. exit returns 0 regardless of execution status
# no file with same name, no directory with same name
cp -f /home/h/Desktop/kernDev/hello1/Makefile .
The if conditional -d is if directory exists, -f is if file exists.
Have fun bash coding. One of my favorite time killers .
Overwriting the old dir will delete its contents. You should always check for existence before creating. Rather than overwrite you should use mv hello$i hello$i.old.
If you are overwriting folders a single typo can cause a ton of data loss.