Fortiswitch T1024E

I intend to use on of  XQ+BC0003-XS+ - breakout cable for connecting one Forti switch T1024E to other three devices like Forti switch 424E, Fujitsu DX600 and FortiGate 601E.

As I understand from Fortinet documentation I must split one port of Forti switch T1024E in four and I do not know how to do it. 

1. On Forti switch, change the split mode:

   This change requires a reboot.

   config switch phy-mode

   set port29-phy-mode 4x10G

   set port30-phy-mode 4x10G

   end

I've connected to it via CLI but it seems that I do not have phy-mode command.

Can anybody help me with some indication?

Manny thanks