Linking Out Archive Items and Archive Blocks to 3rd Party Websites/URLs (linking out a list)

Site URL: https://www.occasionallyuseful.com/

I am looking to link out an archive list to 3rd party sites/URLs. Right now my site allows the links in the Archive Block to link to their respective links in the Blog on my website. However, I arranged the original blog links to be re-directed to the 3rd party site/URL. Someone had suggested that it could be done with a 301 redirect but I couldn't understand how that would work. 

Please refer to the "THEMES" section on this site for the links I am referring to. https://www.occasionallyuseful.com/

Link to video explanation: https://open.yac.com/play/eric_1601938831702