Skarfabakki Harbour to The Old Harbour (Reykjavik, Iceland)

[luv2sleep]

We are taking a non DCL sponsored tour when we get to Reykjavik, Iceland. How can we get from the cruise port in Skarfabakki Harbour to our destination? We need to get 3 miles away to The Old Harbour. I've read on TripAdvisor that there aren't readily available taxis at the port. I don't know what to do. Would something like an Uber be a good thing to set up? I am at a loss here.....Thanks for your help!