Need help calculating acid dissociation constant for this acid?

If they're asking for the dissociation constant, then it will be a weak acid.
Strong acids dissociate 100%, so the dissociation constant would be very large (off scale)

let's see what they mean by dissociation constant:

In aqueous solution, chloroacetic acid splits up into an anion and a proton:

CH2ClCOOH     ---<------->--   CH2ClCOO -       +     H+.

and the Ka = [CH2ClCOO - ] * [H+] / [CH2ClCOOH]

now, we know that the concentration of the anion and the H+ will equal each other. (every molecule that dissociates will split into one of each)
So we can substitute [H+] squared in the numerator,
leading to:
Ka = [H+]2 / [CH2ClCOOH]

If we know the pH we can work out the [H+] , and we're told the concentration of the acid.
so just substitute and solve