A0.1 kg magnet is floating above a second magnet. the magnetic force on the 0.1 kg magnet is

If the 0.1 kg magnet is just hovering there and not accelerating,
then we know that the forces on it are balanced. 

We're particularly interested in the vertical forces, because we
know that there's a constant downward force on it that's due to
gravity ... often known as the magnet's "weight".

It's weight is (mass) x (gravity) = (0.1 kg) x (9.8 m/s²)  =  0.98 Newton.

Since the little magnet isn't accelerating up or down, we know that
the net vertical force acting on it is zero.  That means that the upward
force on it from the other magnet must be exactly equal to its weight ...

            0.98 Newton upward.