Does your current modem/router combo unit have metal trim and tabs around the ports? It would be silver metal (steel) all around the border of the ports, with small like tabs that go into the ports. If so, then ONE grounding adapter will ground all ports, and you should just use our heavy duty shielded Ethernet cables that we carry.
If your modem/router combo unit does NOT have this metal around the ports, pick up a switch (5, 8, or 16 port) that does have this metal. Like this one: https://amzn.to/2IR4vZH
A switch like this can be grounded. If you hook up a desktop computer, the desktop computer will already ground it. Or you can use one of our Ethernet Grounding Adapters and the entire switch will become grounded - all ports :)
Here is a similar switch made by D-Link: https://amzn.to/2QMcHNA
Customer support service by UserEcho