Multiple scsi controller and disk

hello everyone
our VM template setup is
OS: RHEL
Version: 7.6

Our template comprises of 2 disk -
1st disk - 1GB for /boot
2nd disk - 15GB for /, /var, …
The above are all on scsi0

we would like to add disk 3, disk 4 and disk 5 as follows
disk3 - scsi1:0
disk 4 - scsi1:1

disk5 - scsi2:0

We tried using the unit number, but i dont think we are interpreting the documentation very well.

  • unit_number - (Optional) The disk number on the storage bus. The maximum value for this setting is the value of the controller count times the controller capacity (15 for SCSI, 30 for SATA, and 2 for IDE). The default is 0 , for which one disk must be set to. Duplicate unit numbers are not allowed.

scsi_controller_count - (Optional) The number of SCSI controllers that Terraform manages on this virtual machine. This directly affects the amount of disks you can add to the virtual machine and the maximum disk unit number. Note that lowering this value does not remove controllers.

so if our disk 3 is scsi1:0
would our scsi controller will be 3
what would be our unit number?? and how will this correlate to scsi1:0

Thanks everyone