My brother gave Power of Attorney to his friend who is taking advantage of him. What can I do to get POA restored to me?

If you can't convince your brother to make the change, then you may have to go the legal route. Much depends on your brother's cognitive state.
If you look for an attorney, try to find an elder law attorney. You'd probably have to prove the friend is taking advantage of your brother and that what he did was illegal.
Hopefully, your brother can just do the paperwork to make the switch.
Good luck,
Carol

As Carol said, the easiest and least expensive way, depending on your brother's cognitive state, would be to have your brother redo the documents and appoint you as POA. If not you will have to go the legal route which could prove costly.

I have to ask, you state that you want the POA restored to you. This would indicate that at one time you were your brother's POA. If so why did he make the change and appoint his friend. This is a question you will have to be prepared to answer should you have to go the legal route. GOOD LUCK.

Carol's advice is right on except that any attorney can take care of this. Look for an attorney that handles will, estates, family law - not a litigator.