In Fleming's left-hand rule, the forefinger denotes:

In Fleming's left-hand rule, the forefinger denotes the direction of the magnetic field.

According to Fleming’s left-hand rule, stretch the thumb, forefinger and middle finger of your left hand
such that they are mutually perpendicular. If the first finger points in the direction of the magnetic field and the second finger in the direction of the current, then the thumb will point in the direction of motion or the force acting on the conductor.