what do i type for my server ip adress if my lan is already 10.0.0.1
If by lan you mean 10.0.0.1 is the private IP address of your router's LAN interface, then in port forwarding, you give the IP address of the destination system. For example, if you have a computer connected to the router, it might have an IP address of 10.0.0.3. If the target program you are running is on this system and it's listening on TCP port 8585, then you set up port forwarding for TCP on port 8585 and the destination IP address is 10.0.0.3. What this means is that when the router sees incoming TCP requests on port 8585, it will forward them to 10.0.0.3 for actual handling.
If you don't know the IP address of the target system, you need to find out. If Windows, run the ipconfig /all command in a Command Prompt to see the IP address on the active interface. If running a Mac, run ifconfig to display the IP address on the active interface. If running Linux, again, use ifconfig (sometimes /sbin/ifconfig is required, depending on distro and setup). Most systems that run programs for outside connection are setup with a static private IP address so that the IP never changes. If the IP were to change for some reason, the port forwarding definition would then be incorrect and connections would fail.