How far will 350 joules raise a 7kg mass? can you explain the formula used.

When an object gets raised to a higher place, it gets potential energy.
The energy has to come from whatever motor or person is lifting it.

The amount of potential energy it has is

   (mass of the object) x (acceleration of gravity) x (how far it gets lifted).

If the object has 7 kg of mass, and you have 350 joules of energy
to lift it with, then

       Potential energy at the top = 350 joules

              350 joules = (7 kg) x (gravity) x (height)

                             =  (7 kg) x (9.8 m/s²) x (height)

             (350 joules) / (7 kg x 9.8 m/s²)  =  height

               Height = (350) / (7 x 9.8)    (kg-m²/s²)  /  (kg-m/s²)

                         =    5.1 meters