I would like to add a MESH WiFi and move entry point of cable

Our cable comes into a room that is not our office, the TV is there but we have spotty wifi service in our upstairs offices.  The house is brick and there are plaster walls between the router and our offices.  I would like to have the cable brought in to a place closer to the offices, but still available to the TV.  It seems MESH router is the answer.  How do I do this?  should I make an appt for an xfinity service person to come out, should I purchase the MESH router first?  Is the cable that comes into the house compatible with a Netgear Nighthawk AX1800 (3-Pack)?  thank you, I am trying to figure out the order of doing things to upgrade the wifi and make it accessible on three floors. thank you