Opening external links in new tab

Is there a way to force external links to open in a new tab (or even better, a modal)? I have a series of rich-text fields in a list-details block and the links open in the same window, forcing users away from my site.

I found this:, but I’m not technical and I couldn’t adapt it to my purposes. I tried just switching out ‘_self’ for '_blank" but that didn’t work. Can anyone point me in the right direction?

Does anyone have any ideas how to do this?