Assuming you have a "BKUP" Directory in Drive K and the backup files are with the extension .bak and you need to delete all files with .bak in that directory.

Create a batch file that deletes all the required files.

Deleting all files with the extension .bak would need a command such as "DEL K:\BKUP\*.BAK".

You need to create the batch file and have it run in a SQL Server Job scheduled daily.