In the Get items action, use a filter query to where the conversation ID is equal to the conversation of the conversation ID in the trigger. This is more efficient because it is only going to return the item you are looking for and not every item in the list, which by default, is only going to be 100 items. Note, the filter field is the internal name of the field in your SharePoint list and not the display name. So, the filter might be ConversationID eq 'Conversation ID from Trigger in Dynamic Content' and note that the value from the dynamic content needs to be in single quotes since it will be string value/GIUD value.
In the image of your condition, you show the ID field. That is the ID field from the SharePoint list where you are storing the conversation ID. While you don't need this in your condition, the ID in the filter query is the conversation ID and not the item id.
You will still need the condition, but it will not be on the ID. You will use a length expression to find out how many items were returned from the Get items action (ideally it should be one if you implement everything correctly). On the left side of the condition, you will add this expression length(body('Get_items')?['value']) and check if it is greater than 0. If it evaluates to true/yes, send the message.
