Suppose I have acceleration defined as a function of position, "a(x)". How to convert it into a function of time "a(t)"? Please give an example for the case a(x)= x/s²
That's correct except drop the "m", it doesn't belong. Also, there's a general way to do this-- write a(x) = v*dv/dx, use that to derive the work-energy theorem that the integral of a(x) over dx equals the change in v2/2. Solve that for v(x), and say t = integral of v(x) over dx. That gives you t(x), which you can invert to x(t), then plug into a(x(t)). This requires that t(x) be invertible, but it's the best you can do in general.