Thevenin voltage across current source
What, I think, is being asked is for you to find the Thevenin equivalent of the circuit seen by the current source.

In other words, remove the current source and then find:

(1) the open circuit voltage across the port where the current source was formally connected

(2) the equivalent resistance looking into that port.

For example, consider the following circuit:







simulate this circuit &ndash; Schematic created using CircuitLab

The Thevenin equivalent across (or seen by) the current source is







simulate this circuit

where 

\$R_{th} = R_1||R_2 \$

\$V_{th} = V_1 \dfrac{R_1}{R_1 + R_2} \$