If you have a website that's at least a year old and you have over 100 pages, you are almost certainly sitting on an SEO goldmine. Anytime we start doing SEO for a website like this, the first thing we do is go into Google Search Console. This is a free tool provided by Google that shows you what terms you're showing up for and which pages people clicked on.
And the first thing I like to do is sort by impressions. So this will show you what terms people are typing into Google before your website shows up in the search results, whether or not they click on it. I like to think of impressions as opportunities.
It might not be actual traffic to your website, but it's showing you that you could get traffic from those terms if you were ranking a little bit better for each of those terms if it's relevant to your business. First determine if you're already using it in an existing heading tag. If not, simply adding it to an existing heading or the H1 of a new page is probably enough to start getting traffic.
If you are already using those terms in an existing heading, try refreshing that page. Optimize your heading tag, use formatting like bullet points and tables, add some relevant data points, facts, statistics, and consider adding the current year to the title. Just don't change the URL.
Then submit the page to Google Search Console to make Google, crawl the page and check back in three weeks. See if traffic's picked up.