Ubuntu – What does “paths must precede expression” mean when using find

tl;dr Always quote globs in find: find . -maxdepth 1 -type f -name "*.jpg" (notice the " characters surrounding *).

In your case, the shell is interpreting *.jpg (note the * character) and trying to match file names within the current directory that end in .jpg. There is a file named pic1 (1).jpg so that file name replaces *.jpg. The command the system is given by the shell becomes

find . -maxdepth 1 -type f -name 'pic1 (1).jpg'

To see in depth, try tracing the original command using strace. What is actually executed is:

touch foo.jpg bar.jpg
strace find . -maxdepth 1 -type f -name *.jpg 2>&1 | grep jpg
execve("/usr/bin/find", ["find", ".", "-maxdepth", "1", "-type", "f", "-name", "bar.jpg", "foo.jpg"], [/* 62 vars */]) = 0
...

You were right in considering -execdir. Something simple like the below should work

find testfolder/ -name '*.nef' -execdir mkdir -p NEF \; -execdir mv {} NEF/ \;