Noob question, we switched routers, IP addresses now all different, can't find Linux server anymore. Please help?

Normally I'd ask my IT guy, but he's unreachable.

He built a Linux server that acted as a proxy server and also hosted our local wiki, which is just a simple wordpress site. Users here at work could just type wiki into the address bar and it would appear at http://wiki. It was great.

If it ever went down, he would access it through something called proxmox if it ever needed restarting. The instructions I have to access proxmox are to just type the old IP address into the address bar of his computer, and it was one of the options. However, we had to change routers and all the IP addresses are different, and now the server is no longer at the old IP address, so of course that saved address doesn't work. I can't figure out how to find the server on the network, and to even be able to view any web pages at all, I had to turn off the "use a proxy server" option in the browser like I had to on all the other computers, which means I assume the proxy server is not functioning.

Where would we start in terms if figuring out how to access that server or figure out it's new IP address? Honestly, I just want to get the wordpress site off of it, it's our wiki, and we could likely figure out how to host it another way. I just don't know where to start. Thanks in advance.