A lewis base is an electron pair donor, out of acetonitrile, DCM and methanol binding to a metal complex centre.
I'm guessing that acetonitrile will be the strongest lewis base as its got high electron density on the nitrogen followed by methanol due to lone paris on the oxygen atom then lastly DCM which is weaker at co-ordinating to the metal centre due to electronegativity of chlorine? is this a correct approach?