Command Only
:DISPlay:TRACe{Tr}:Y:SCALe:AUTO
This command executes y-axis auto scaling.
10 OUTPUT 717;":DISP:TRAC1:Y:SCAL:AUTO"
:DISPlay:ATRaces:SCALe:AUTO
:DISPlay:TRACe{Tr}:X:SCALe:AUTO
Auto Scale > Y OR
Right-click on the graph plot > Auto Scale Y