add a space/split up pairs of characters

Notepad++ has very limited regexes so you have to use something like this:

Search for

(..)

and replace with

\1 

(Note there is a space after the \1!)

(..) means find two characters and store them

\1 get the characters stored in the first capturing group

Precondition for this simple solution is that there are only such strings and nothing else. And it will then add an unneeded space after the word. If this is not not wanted you can remove it afterwards.

I don't have Notepad++ installed here, but on my editor you can search for \B(?=(?:[0-9A-F]{2})+\b) and replace all with a single space.

Explanation:

\B            # only match within words
(?=           # Assert that from the current position...
 (?:          # ...the following can be matched:
  [0-9A-F]{2} # a succession of two hexadecimal digits
 )+           # once or more,
 \b           # ending at a word boundary.
)             # End of lookahead