Found an old wordpress blog

After digging up an old niche I was involved in years ago I've found a 4 year old wordpress.com blog with 6 articles related to my niche. The articles have no incoming, outgoing links but, does get some traffic. I was thinking of adding a link to my new website in the sidebar, or should I add it within the articles content if so how many or should I not bother as it could hurt my new website?

chrome tracks if links have traffic.

Use semrush.com to look for any toxic links on this old website.

If it has no toxic links, then I think you are safe to add a backlink to your money site.

Remember to add a backlink on tge homepage of the website.

should I add a site wide sidebar link or just the one on the home url?

It is safer to go with contextual links. It adds more value. You should be careful with sitewide links because Google may see this as spam.