Generally IF output is the output of the mixers, so up converted signal can be provided from this port.
LOSC is as usual to drive the LO signal and finally RF port is used to insert the main signal to be up converted.
This is valid only Gilbert cell based mixers.But in diode based mixers, RF and IF ports are interchangeable.
But technical data should be carefully studied because some restrictions/constraints can be applied especially transformer based diode mixers.