In order to scan for SSH ports in a particular subnet, use the following command
sudo nmap -sS -p 22 <target>
The following is an example.
sudo nmap -sS -p 22 192.168.1.0/24
The 0/24 declaration defines the length of the subnet mask. Without going into too many details, this simply means that it scans the last 256 address from 192.168.1.1 to 192.168.1.255.
The following is an example output
Starting Nmap 7.94 ( https://nmap.org ) at xxxxxx
...
Nmap scan report for 192.168.1.2
Host is up (0.0090s latency).
PORT STATE SERVICE
22/tcp open ssh
MAC Address: xx:xx:xx:xx:xx:x (ABCD)
...
In this example, port 22 (SSH) is open on the IP address 192.168.1.2.