SCSI harddisk installation.

I got a ML 350 G2 Compaq server with Os as NT 4.o.The existing system has 3 18.2 GB Ultra SCSI 3 H/D wich is configured with H/W raid.I want to Install 3 more harddisk inorder to increase my storage capasity.I supposed to purchase three 36 GB SCSI hard disk.How should i configure this hard disk?Weather i can configure one more raid ?(I think i had only one raid controller).Please advice me or else please provide me a some site address in which i will get all the details.