How can I convert D&D 4e adventures and settings to 5e?

At my public library, I have ready access to resource books from older editions of D&D (only 5e are in heavy demand). Most of the books at the library are 4e. I am interested in converting some of the adventures and/or campaign settings for use with the 5e group I DM.

How can I convert these 4e adventures to 5e?

My background is a few years playing and DMing AD&D back in the 80s, then nothing for 35 years. I fiddled with the 4e beginner’s set and now play 5e.

I have no experience converting. Currently my group is playing HotDQ. They enjoy it, but I find it a little railroad-y and want to expand the world.