rename a range of files using one-line command

for files in filename* ; do new="prefix_$files" ; echo "$files $new" ; done

you don't even need the new="prefix_files";

you can
for files in filename* ; do mv $files pre_$files ; done

and make it even shorter

root@msu:~/haha# for files in haha* ; do new="prefix_$files" ; echo "$files $new" ; done
haha1 prefix_haha1
haha2 prefix_haha2
haha3 prefix_haha3
haha4 prefix_haha4
haha5 prefix_haha5
haha6 prefix_haha6
haha7 prefix_haha7

i would like to help you but not here this is my mail mtalamu8@hotmail.com