Lets say you have your first ESB located at ESB01_HOME directory and it contains all your defined proxy services, endpoints and other configurations. Now you took another fresh copy of the WSO2 ESB and extract that to a folder called ESB02_HOME.
You can copy the configuration files which were stored in ESB01_HOME/repository/deployment/server/synapse-configs/default (entire folder) in to the same directory in the ESB02 (ESB02_HOME/repository/deployment/server/synapse-configs/default). Now you can start the ESB02 and you can observe that all the configurations are installed in the ESB02.
If you are starting both the servers (ESB01 and ESB02), then you need to change the Offset parameter of the ESB02 carbon.xml configuration file which is located in the (ESB02_HOME/repository/conf/carbon.xml)
If you are copying the configurations from an older version of WSO2 ESB (3.x.x) then these configurations are located at ESB01_HOME/repository/conf/synapse-configs folder.