In case you are wondering how to rename multiple files in bash here is an idea:
for file in ?????*; do mv $file `echo $file | cut -c4-`; done
Whit this you can cut 4 characters from the beginning of the file names which are at least six characters long.
Btw, this will NOT work if you have spaces in your filenames, but to solve this you can issue the command below replacing spaces with underscores:
for file in *\ *; do mv $file ${file// /_}; done
Enjoy 😉