Assuming that you're given either an initial or final velocity, you can use the following equation and solve for the initial or final velocity.
Vyf² = Vyi² - 2g(y - y₀)
Where,
Vyf² = final velocity
Vyi₂² = initial velocity
g = 9.81 m/s²
(y - y₀) = the change in the distance along the y-axis.
You'll need also determine the positive and negative of your y-axis for your final solution because velocity can be positive or negative based on direction. Lastly, don't forget to square root both sides of your equation for your velocity.
I hope this helps.
