Okay, whew! that makes a bit more sense. Honestly, if it's a 192.168.x.x address, you are safe posting it since it's just an internal address so none of us can get to it.
The first thin to try is to use the same ftp client and try to connect to "retropie" instead of "192.168.1.100" (example IP address). If you don't set a static IP address, the Pi's address can change from time to time. There isn't really a problem just using the name retropie instead of an IP. If it stops connecting at some point, it's usually after a power failure and rebooting the router can clear it up.
If you would like to look further into say setting up a static IP address can you please let us know what type of router you have? I can probably dig up an online tutorial on how to get in and change stuff like that for you.