Do you mean on Firefox's address bar, where the URL displays, or in a web page form that needs you to enter your address?

For Firefox's address bar, the categories of data shown in the drop-down are set on the Options page, Privacy panel. See this article for more information:

Address bar autocomplete suggestions in Firefox - go to the "How can I control what results the location bar shows me?" section

For forms in web pages, if you want to completely turn off form autocomplete, you can do that also on the Options page, Privacy panel. See this article for more information:

Control whether Firefox automatically fills in forms

Does that help?

The location bar drop down list can show history items as well as bookmarked pages and websites currently opened in tabs. You can set what suggestions to show when you enter an URL in the location/address bar in "Options/Preferences > Privacy".

• Tools > Options > Privacy > Location Bar: When using the location bar, suggest:
  History
  Bookmarks
  Open tabs

The browser.urlbar.suggest.history.onlyTyped choice needs to be changed directly via the pref. The browser.urlbar.suggest.searches choice is present in Firefox 43 and later as "Show search suggestions in location bar results" in "Options/Preferences > Search" as part of the search settings.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config