[Theme Horse Support Team]

Hi [email protected],
If you are not able to remove the old plugins from the old plugins then there is only one way to delete it from ftp, You just login to the ftp and inside ftp there may be public_html or other
Go to public_html -> theme folder(WordPress) -> wp-content -> plugins

Then delete the plugins which you are not able to remove the plugins. And after doing this you can simply add a latest version of plugins from the dashboard.

Thank you!