Depending on configuration options you put in the start up script, There will be an option to specify the map location, for example one of the servers i run uses something like below. You can ignore the -ip unless you run multiple IP's on your system.

valheim_server -nographics -batchmode -name "Yourservername" -ip YourhostIP -port 3456 -world "YourSavedMapName" -password "yourpassword" -savedir D:\Valheim-Node3\Gamesave\ -public 1

If you don't specify a -savedir, you will need to navigate to C:\Users\yourlogonname\AppData\LocalLow\IronGate\Valheim\Worlds\ and copy your generated map (the .db and the .fwl). You'll then need to make sure the -world "YourSavedMapName" is changed to match the name of the .db/.fwl file. That's it, there is also a PDF in the installation directory that explains these options in more detail.