Manage how long history is kept

I use a website often where the links on any given page change colour if I have previously visited that page referenced by that link. This was an easy way for me to keep track of which pages I have accessed before. In the past, Firefox would retain this information so that I could see where I had been even if I last visited the site several years in the past. At present, if I visited the site more than 6 months ago, I can no longer see it. How can I change the settings so that my browsing history is retained indefinitely?. I have backups of the AppData profile folders which I'm hoping that I can restore once the setting is changed so that I can once again see my history on this website. Greg