Only this one:
https://addons.mozilla.org/en-US/firefox/addon/adblock-plus/
(PS: Don't tell the Ed!).
However if your ads are appearing as pop-up, no ad-blocker will help. They're caused by malware. To deal with them download, install and run the free version of Malwarebytes:
https://www.malwarebytes.org/free/
Points to note:
1. When installing, take care to deselect the option to install free trial of the 'PRO' version ;
2. When running it, use the 'Quick scan' option ;
3. Don't be surprised when that 'quick' scan takes over half an hour to finish ;
4. When it does so, click the button to view the results, ensure that there's a tick alongside everything listed and then click the button to delete what's been found.