Please follow the following steps
The object is thrown so it moves up with an initial vertical velocity of
Ignoring air friction horizontal component is horizontal motion with constant velocity.
Vertical component takes the object up, reduces due to acceleration due to gravity acting in the opposite direction, becomes zero at a particular instant. Thereafter, the object falls freely.
As both the components are orthogonal these can be treated separately.
Now Vertical displacement
When the object reaches ground we have
Applicable kinematic equation for vertical displacement and other quantities of interest is
Resultant velocity is sum of
In vector notation we have selected
Alternate method of finding vertical component of velocity as the object hits ground.
At the time when object is thrown upwards, its total energy is
As it hits ground all the energy is due to its
This equation gives you the same result