It looks like you're conflating the syntax for direct editing in the myaliases.alias file and the import syntax for the FARR options GUI.
Try creating a new alias entry in the FARR options GUI.
Go to FARR help > program options > Lists > Aliases... > myaliases.alias and click the "Add a new Alias" button and enter these
Alias trigger:
grep
Score:
1000
Regular Expressions pattern:
^grep (\S*) (.*)
Results:
grep $$1 $$2 | C:\Users\user\AppData\Roaming\Saleen Software\Saleen ScanFs\ScanFs.exe /path="$$1" /contents="$$2"
Also, try the below command in Windows cmd, but replace <file path> and <search string> with something useful. If it doesn't work look up the correct parameter syntax for ScanFs.exe
C:\Users\user\AppData\Roaming\Saleen Software\Saleen ScanFs\ScanFs.exe /path="<file path>" /contents="<search string>"