How to see data usage across devices

Recently our data usage has spiked over 500 GB of data, and is now at 1.1k GBs, which is not normal or good and we have a very scarce amount of data left. 

I have been trying to figure out how to see what devices are using data and how much, I have gone through the xfinity app, I have gone into the router IPV4 gateway and whatnot, but I still cannot find a single answer and a single statistic. Can somebody please help me figure this out?