FileMaker has a slightly different path syntax from AppleScript (Mac)* paths. It has a prefix "filemac:/" for absolute paths, and the directory separator is "/" (not ":"). I recently created this little subroutine to convert them. Example (you'd use your AppleScript Mac path instead of the 1st 2 lines; mine below is the path to your iPhone xml data file, which has all the paths to the pictures):
set picts_path to path to pictures folder as text
setxml_pathtopicts_path & "iPhoto Library:AlbumData.xml"
set FM_path to "filemac:/" & my ConvertPath(xml_path)
set AppleScript's text item delimiters to ":"
set x to Mac_path's text items
set AppleScript's text item delimiters to "/"
set z to x's text items as text
set AppleScript's text item delimiters to ""
You can just set the resulting FileMaker syntax path (could also be "imagemac:/" if you want to see the PDF) into a FileMaker cell (of the current record); for a reference to the file.
*There are also Unix paths on a Mac. Which use the slash. But don't include the drive name (which you really should have in the path). They can also be converted, by having the Finder (or System Events) get the startup disk name and tacking it on the front.
Basically each syntax path can be converted to the other. Conversely most non-simple operations integrating different scripting systems seem to require different syntax paths somewhere. Just one of those things :-]