Assuming your files are all starting with DIM
@echo off
setlocal enabledelayedexpansion
for /f %%i in ('dir "*.TXT" /b /a-d') do (
set "var=%%~ni"
echo ren !var!%%~xi !var:~0,-9!%%~xi
)
Once you can confirm that it does what you want, and ONLY then, remove the echo
from the last line to actually rename the files.
Important Note. If you have files with similar names, but different date entries, this will not work as you think. as Example:
DIM2_UPI_20170910.TXT
DIM2_UPI_20170908.TXT
The names are the same, but dates differ, making each filename Unique. If you rename them, there can be only 1 DIM2_UPI.TXT
So as long as you understand this, you will be fine.
Edit: based on Amazon drive question. Note you need to change the directory portion to how you access amazon drive.
@echo off
setlocal enabledelayedexpansion
for /f %%i in ('dir "DIM*" /b /a-d') do (
set "var=%%~ni"
echo ren !var!%%~xi !var:~0,-16!%%~xi
)