If you’re more into YouTube video tutorials, check out RJ the bike guy

Dowels work too if you’ve got them. I use that method for concrete too, since I find tapcons frequently fail to grab. Drill out the concrete hole larger than the screw. Shove a dowel or a bunch of toothpicks/splinters into the hole, then drive the tapcon or a wood screw in. Holds like crazy since the wood conforms to the concrete wall imperfections. Might rot over time though. Maybe plastic is better.

Check out RJ the bike guy on YouTube for great repair videos for old bikes.

Here’s an example if you need to change out the calipers with a different mounting system.

https://youtu.be/74RBbMoAy4k