remove only *.dat and *.csv files older than 4 moths
find /path -type f -mtime +120 \( -name '*.dat' -or -name '*.csv' \) -exec rm '{}' ';'
or move the files, but please be aware if destination is wrong or some bad happens then you'll lose files
find /path -type f -mtime +120 \( -name '*.dat' -or -name '*.csv' \) -exec mv '{}' /destination/ ';'
