robin [connect 192.168.7.2 3000(
The 192.168.7.2 is definitely the IP address of the board when connected over USB.
When on the wi-fi network, your board will have a different IP address. If you have access to the router for the wi-fi network, you can check what the IPs are of each of the devices connected. Any half-decent router will allow you to assign a static address to each wi-fi dongle, so that the IP is guaranteed not to change when you reconnect.
Alternatively, you can find the IP from Bela itself: connect over USB and run
ip a. Next to
wlan0, you will see the IP address that the board has on the wi-fi network. While it is likely that the router will re-use the same address next time the same wifi dongle connects to it, there is no guarantee (unless you do as explained above) that it will persist.
You could also try to send messages to the broadcast address of the wifi network (typically xxx.xxx.xxx.255) to attempt automatic discovery, but hopefully the static IP method above will work and it is much easier!