select disk 3
create volume simple (creates volume on the whole of the selected disk)
select vol <new volume>
format L: /FS:NTFS (the good old way of full formatting)
The clean and the cleanall will do every sector of the entire HDD it's pointed at, it will not do single partitions, all data on the HDD will be permenetlly over-written; have a look through these tutorials linked below for some ideas.