I would expect that such a big network has some kind of structure, that divides the network into segments
example
head-office/campus = 192.168.1.0-192.168.100.254
sub-location = 192.168.101.0 - 192.168.101.254
shop 1 = 192.168.102.0 - 192.168.102.254
...
VPNs/WFH = 192.168.200.0 -192.168.202.254
So you can ask for that structure and can map location and IP to one device, then at least you know where to search it...
in some companies there are smaller network segments, that you even can divide it into buildings or floors...
in a bigger location you might be able to check the connection from a network device => several years ago it was possible with managed CISCO switches to do such inventory by run scripts on the switches, find the IP or MAC of that device via commandlines in the CISCO OS => then you know to which switch and switch-port the device is connect to, switch-location = device-location.
several years ago I scripted something like that in VBS/VBA and got an Excel as an output.
I'm the project manager trying to find a solution, but they are not using any tools to locate the PCs. Can you tell me more about the monitoring tools?
Thank you