Rename all files which contain the old sub-string, replacing it with the replacement sub-string.

rename old_value replacement_value directory/filename

for i in ./*foo*;do mv -- "$i" "${i//foo/bar}";done

rename 's/ /-/g' *

As long as you have perl based rename.

You can check:

rename --help

or

rename [-v] [-n] [-f] perlexpr [filenames]