You can probably do something called a small estate affidavit. The power of attorney is no longer effective—it terminated when the mother passed away.
It will be easiest to have an attorney assist with this and it should not cost too much. An attorney can take a look at all the paperwork to make sure that is really the best approach. If a small estate affidavit is the correct approach, an experienced attorney will be able to get it done for you much quicker and easier than trying to do it yourself.