How to change filepath structure using automator (windows to mac)?
Blank spaces have to be escaped. To escape a special character, like a blank space, you use a forward slash, so " " will become "\ ".

You can modify the script, https://gist.github.com/2211017, link to from the post you linked to by adding the following line set mytext to searchReplace(mytext, " ", "\ ") after line 16.

...
15. set mytext to searchReplace(mytext, "&gt;.", "")
16. set mytext to searchReplace(mytext, "&gt;", "")

17. set mytext to searchReplace(mytext, " ", "\ ")

18. set findIt to "\\"
19. set replaceIt to "/"
...