Cuffuf

Okay so as a bit of a newbie to all this I need a bit of help with setting up auto restart. I would like to have it automatically send out a message at a certain time of day saying it will restart. I plan on using User scripts, which I have already used a bit. Here is the problem: I have no clue as to the command I need to get to the minecraft console and then to do "say Restart in 10 minutes". If you look at the bottom of the attached image, that is what I mean. I just want to say that from the actual web terminal of the whole server. That way I can just turn it into a User Script and schedule it. I already have commands for restarting the docker container and the whole server, it is just that very specific command I need to figure out. My knowledge about this stuff, especially console commands, is very limited. Any help I can get is greatly appreciated!