mv: cannot stat error : No such file or directory error

Normally, when a glob which does not match any filenames is expanded, it remains unchanged. Thus, you get results like this:

$ rm .bak rm: cannot remove `.bak’: No such file or directory

To avoid this we need to change the default value of nullglob variable.

    #BASH

    shopt -s nullglob

    for i in dir1/*.txt_dir; do
       mv $i/*.txt  dir2/'basename $i'.txt
    done

Read more about it here: http://mywiki.wooledge.org/NullGlob

Hope this helps!