Can't find my proxy server's files

inside my folder with velocity.jar and start.bat am i supposed to find a sever file since in the docs it said to put online-mode for every server but i cant find the server properties nor my server’s files

Have you started the server before?

yes i have started it

I guess you mean to disable the online mode for every minecraft server, like spigot or paper. You have to go to your minecraft server’s directory and set online-mode in the file to false.
If you want to run velocity in offline mode, go to velocity’s folder and set online-mode to false in the velocity.toml file.

no like the servers inside the proxy