But, pedantically, note the initial phrasing of OP's post DOES appear to specify a replacement:

my goal is to replace C:\Program Files\180searchassistant\salmhook.dll to a custom file name "C:\japansese characters\japnaese character filename.exe"

.

nonetheless, ++ for the portion of your post re the backslash...

and re OP's problem with multiple instances of "However I can't do the replacement globally because ... there are 2 places that hold filenames. " one might suggest that:

• if OP knows the replaceable-instance always comes first, a simple regex, applied NON-globally (ie, *WITHOUT* a /g) should do the trick
• if placement of the replaceable-instance is unknown or variable, my first thought would be to see if some other defining characteristic (context, for example) might be used in the regex

FWIW....
ww