Transportation Guide/Help in Barcelona

Here is the website for the Barcelona Transit Authority, the TMB.
https://www.tmb.cat/en/home
You can use the journey planner on the home page to see how to from point A to point B.
There are other resources like Metro (subway) map. Bus maps. ticket prices,

PS, just put in your example and got directions and a map to take the 34 bus plus 400 meters total walking will get you there in 12 minutes. I am sure they also have an app for your phone.

Are you comfortable using Google maps? There are bus, metro and walking directions options. The metro and bus options include the line name or number that you need. Plus any walking. Plan a route on maps, then confirm on the transportation website previously provided. Using the metro is very easy. Get your ticket at the machines before the turnstiles (The one way ticket is good for any connecting route until you exit a station). Insert your ticket at the turnstile. Find the correct platform. Once aboard, watch the route display inside the cabin. Try a route once in Spain, give yourself extra time to allow for mistakes. Once you have done a few, you will get the process.

Your hotel concierge can give you a lot of help with these questions.

You can go on Google Maps and enter the addresses you want to go to and from. And you can print out the details that give you directions on foot or on public transportation.

I use this constantly. Before I go into any neighborhood in any new city, I actually know where I'm going and even where the restaurants in the neighborhood are.

We've been to Barcelona, and taken the subway to our hotel up by La Sagrada Familia. I'll admit it took a couple of transfers that might have been confusing to someone that's not familiar with underground travel.

When all else fails, you can rely on Barcelona's taxis, they are inexpensive, safe, and plentiful.

Barcelona is also a great walking city, don't underestimate the power of your own legs!

YouTube can be great for pre-travel orientation. The “road trip Spain and Portugal” channel has good guides for transit orientation—I’d imagine that includes Barcelona.

We use the on/off bus. It goes to all of the big sites in town. There are two lines. They run till 7:00. They will stop at the places you mentioned, and when you are done, they will stop again and pick you up and you can continue to whatever stop is on the route. The blue line stops are: Placa de Catalunya, Casa Batllo, La Pedrera, Sagrada Familia, Sant Pau Recinte Mondernista, Park Guell, Tramvia Blau-Tibidabo, Sarria, Monestir de Pedralbes, Pavillions Guell, Futbol Club Barcelona, Diagonal Les Corts, Francesc Macia-Diagonal, Eixample-in that order, then repeats. Check out each site,online, to see if you want to stop. About 37 euros a day or cheaper for two-day pass. They also have headphones on the double decker buses, describing the sites they go by, so you get a little history lesson on the way. Open air top deck is my favorite.
It may be cheaper to use the city buses, but this was less confusing for us. They run very frequently.
The Red line stops at the world trade center, if you are laying over on a cruise. No luggage is allowed. :( You can go on both bus routes, during your day. They also cross over with each other at Placa de Catalunya, Casa Batllo and La Pedrera. Just cross the street and look for the on/off bus sign to get on the bus. We use this a lot, when we travel. It's cheaper than the cruise ship tours, as the admission is usually cheaper at the venue.

Barcelona is one of Europe’s cheapest taxi cities. They’re everywhere. We found the subway to be less convenient although we did use it a couple times.