Hi Maung Tan,
When you enable SSH service using "set system services SSH" , SSH will start running on port 22 and you cannot change that.
If you want to block connections to port 22, we can use firewall filter or if you want to use some other ports to do SSH, we can use destination NAT rule to redirect requests coming to any other ports to port 22.
Thanks,
Suraj
If this worked for you please flag my post as an "Accepted Solution" so others can benefit. A kudo would be cool if you think I earned it.