How to quickly rename files on NAS
Running for over the results of a find is not recommended, it will break on filenames with spaces, newlines etc.
You can use the following instead once you are logged into your NAS:
find /share/Public/ -depth -name '*:*' -exec sh -c 'mv -- &quot;$1&quot; &quot;${1//:/_}&quot;' _ {} \;

To be on the save side, run
find /share/Public/ -depth -name '*:*' -exec sh -c 'echo mv -- &quot;$1&quot; &quot;${1//:/_}&quot;' _ {} \;

and check the output for anything unexpected.
PS: The duplicated // in ${1//:/_} is intentional to ensure that all occurrences of : are replaced.