How do I multiply gravity with mass in finding potential energy with the equation pe=mgh

That's it! That's all you need to do.

The formula for gravitational potential energy is

PE = (mass) x (gravity) x (height).

- - Where it says 'mass', write the mass of the object.

- - Where it says 'gravity', write the acceleration of gravity

on the planet where you are. On Earth, it's 9.8 m/s².

- - Where it says 'height', write the height of the object above

the floor, or above the ground, or the roof ... whatever.

When you put those numbers in and do the multiplication,

the answer you GET is the object's PE.

The neatest part is: If you put in the numbers with SI units ...

mass in kg, gravity in m/s², and height in meters ... then you

don't need any more numbers, like constants or conversion

factors etc. The SI units all work together, so that the answer to

the multiplication of those 3 numbers IS the PE with units of joules!