Look at figure 3. (Gate-to-source voltage vs. drain-to-source current.)
Does it mean if I put a 5 V voltage supply attached to the gate and the source, the mofset will generate a source-drain current of ((-5 -(-3)) V * 5 S ) = 10 Amps ???
It doesn't generate any current, but it can control the current. FET devices require very little gate current, so they have "essentially" infinite current gain. (But, they really are not "current gain" devices, since the "output" current is a function of gate voltage.)