Different plc manufacture connect into one pc

Dears,

I get four different plc manufacture control four different factory lines. Now I plan to make monitor throught one scada install at one PC What is protocol tyoe output port usually? Is it Modbus tcp / IP or Ethernet / IP? I plan to connect whole four plc into one Ethernet switch get four ports then into one scada pc get opc server Am I in right way??

Please advice Best regards John