Trying to move my files from old computer to new

I have an old iMac 2009, and the version is macOS High Sierra version 10.13.6. I recently purchased a new iMac, not sure of the version. I am trying to use the migration app and both computers are connected to the same WiFi, yet they wont connect. The new computer shows the old computer but it wont connect. Says its unable to connect. What am I doing wrong and is there something extra I need to do on the old computer so the new one can connect to it?