If you think your dog might have lice, the best thing to do is to go to your vet. They can do a full physical examination, and check your dog over from nose to tail! If there is a risk your dog may have lice, your vet will prescribe a treatment suitable for your pet, which should eliminate the lice. They can also help you plan a parasite prevention plan going forward too, to make sure your dog stays protected, and talk to you about how to clean items like bedding to help prevent reinfection.
If there is any doubt, your vet may recommend skin tests. These will look for the lice, which can be more easily identified under a microscope.