Hi there @Yvonne   You have the option of adding a tag to these conversations and then configuring a temporary workflow to close out these uniquely tagged conversation.

If you have more than a handful of conversations that need to be updated and you don't want to manually select them, you could also use the REST API to perform bulk updates to conversations, including closing, replying, snoozing, and assigning conversations. To do this, you will need a list of the conversation IDs for your chosen criteria. You'll find more on the Update a conversation PUT method in our Developer Documentation