Current to Voltage Gain using Network Analyzer
Most network analyzers require a voltage input, so you'll likely have to use a load resistor and calculate the resulting transconductance based on the resistor value.

[Edit based on The Photon's correct comment below]:

If the analyzer has 50 ohm inputs and the inputs can accept your current range without violating its specs, you can use the 50 ohms as your load resistor and calculate the transconductance from that.

If you have an analyzer with a high impedance input option, or you need to use an active probe because your current puts you outside the range of the analyzer, then you can use an appropriate load resistor.