Beneficial millipedes around cottage.

How do we get rid of large amt of millipedes around foundation of our cabin.

You may have a more serious problem that is attracting the millipedes.  They are voracious predators of other insects.  Eliminate vegetation around the foundation, clean the rain gutters and downspouts, make sure perimeter drains are clear.  You need to reduce excess moisture.
Health Canada has some good information here:  http://healthycanadians.gc.ca/product-safety-securite-produits/pest-control-products-produits-antiparasitaires/pesticides/tips-conseils/sowbug-cloportes-eng.php