I have an old pc. The monitor doesnt work anymore. To be honest I don’t even know if the pc is on as no one ever uses it anymore. I have a modem and a router, and several wireless devices. My question: can I get rid of the PC? If so how would I configure the modem and router. I (for many reasons) don’t go in that room right now. I want the two devices out of there, and to find a way to dispose of the PC. I suspect I don’t need the PC, but as this is how we’ve always been set up, I don’t know.
You can pretty typically configure modems and routers via a web-page interface (using a browser).
It really depends on the wireless devices you have and your router.
I can control mine from my phone (indeed, the setup routine is made to be done using your phone).
But, different manufactures are different and do things differently.
In general, it is usually good to have a PC/Mac on the local network so you can login and troubleshoot problems. A phone might work but, usually, not as good. Mine can but, even so, I’d want a PC/Mac on the local network if I really needed to get into things.
ETA: I actually do need a PC/Mac to configure my router.
As for getting rid of the old PC, check your area for e-waste recycling services.
If there’s a Best Buy retail store near you, you can take most old computer equipment there for recycling. I just took two ancient desktops to my nearest store, and they took them with no questions.
You should be able to check if the PC is on by listening to it. If it’s on, then there should be some kind of fan noise. If it’s been sitting there for a while, then there’s a good chance it’s off from losing power during a random power outage. Unplug it and see if anything stops working. If you go a month without any problems, then likely the PC isn’t being used for anything.
Is this in your house? If so, who set it up in the first place?
Also, what are the odds thre’s sensitive information on the hard drive? Photos, banking info, emails, etc. Depends if you trust the disposal site…
Computer disposal 101: take out the hard drive and make it unusable - hammer it good, drill through it, smash the circuit board on the back of it, or something. If you are a bit more advanced, you could plug it into a different computer (depending on how old) and at least copy/delete old info. Although, actually deleteing items on a drive does not much unless you get really techincal with a wipe program.
By modem I assume you mean internet connection, nobody uses dial-up any more. 
These should be configurable from the web page of the device. You can figure out the web page address from a phone, in my iPhone the settings - wifi-then the circled “i” for the used network tells me the IP address and the IP of its router. Unless your modem is your router (like some new internet suppliers) there’s not much to configure on the modem.
Generally the router plugs into the internet modem, which then connects to either cable or phone line, depending on your internet provider. As long as you have another place to connect the modem, you can just unplug it and move them. Both should retain any settings, otherwise you’d be SOL the first power outage you’d had.
Just remember, if it’s a phone line connection - some connections the phone company use a line filter (a little device half the size of a matchbox) that plugs between any phone and the wall that filters out the internet signal background noise. Obviously, you have to remove that filter if you plug the modem into that wall socket.
And of course, consider where you put the router if it’s your source of WiFi. Going through big thick construction (like a fireplace and chimney) will block a signal’s strength, as will metal appliances. Don’t hide it so the line of sight signal to where you typically use wifi has to go through a that sort of blockage. Center of the house is best to get signal everywhere, but nowadays even a corner of the house actually usually works OK. (If there’s a low signal spot, you’ll figure that out soon enough)