As you exit the baggage area and Customs, you'll see several taxi stands. The "Remisse" services are the most secure, and the most expensive. Unfortunately I now forget what the fares are from Callao (the district where the airport is located) to Miraflores, but I'm guessing it will be at least US$40, maybe $50? Perhaps another poster can help with that question.

There is also a stand for Taxi Green, which costs much less and gets you a less luxurious ride, but is still quite secure.

I do not recommend taking street cabs from Callao to Miraflores, or Uber for that matter, especially if you don't know Lima well and/or don't speak Spanish. Callao is not a safe district and tourists are targeted by thieves, especially at night.

Enjoy Lima, despite the security issues it's a wonderful city in many ways.