Site Down Over Night

Hi, forgive my ignorance, I took over the running of a site I worked with recently so I do not know many of the details.

The site I took over running was working last night, but this morning when I attempted to sign in via

URL.com/wp-admin

My browser doesn’t seem to be able to connect to the server, how do I find out what my URLs server is? and find out if the domain is no longer active?

I’ve spent the last two years of my life working on this and would be devastated if I could no longer access my work. Any assistance would be greatly appreciated.