So you need to search a single directory for all files older then x days, compress them and remove the originals?
Let's start by printing files in a directory that are older than let say 30 days:
find . -mtime +30 -print
Now here's how you find all files in a given directory that are older than 30 days, the tar them and then delete the originals in a single command:
tar -cf files_older_than_30_days.tar --remove-files `find . -mtime +30 -print`
Please notice that before find . -mtime +30 -print I used back tick ` and not an apostrophe ’.
Have you ever wondered how to enter a back tick on an iPhone or iPad?