We will use simple formula for velocity with constant acceleration.

and formula for path

where:
v0 - initial velocity
a - constant acceleration
t- time
x - path
x0 - initial position
v0, and x0 are equal to 0 in this case, so we can simplify our formula to

and

We can modify first formula to get time

and substitute it to second formula.
Now we can find acceleration

m/s