You can access it via
Serial port or
Console cable. But you need to know username and Password. But it should be a manageable switch.
Generally switch has no ip address and if it has ip address that mean it should be in device management vlan. Firstly check your device management vlan ip address range.
You can find mac address using IP scanner tool. Most IPscanner tools are shows switch mac address with devices ip address. This process will be time consuming because you have no idea about subnet or ip address range.
If it is in vlan and if it is connected with another switch such as core switch you can find it within core switch. In cisco you can use '
show cdp nei detail' command.
If it is not a manageable switch don't think about ip address or subnet.....