I am unsure of your intent. Please clarify. Your wording indicates you want to delete them,

I should have been more specific. You're correct, I do want to delete the emails from 2018 and before. TU.

Ok, highlighting and pressing Delete key is probably not the solution you seek, so I presume there are many messages to keep, and others to delete. You could create a filter that selects a date range and set the action to move to trash. That would let you selectively empty from that time frame. Or am I still misunderstanding?

How do I do that. I see the Quick Filter box, or do I need to go somewhere else.

go to tools>message filters. There, create a filter for manual running that is always true, e.g. subject does not contain xxxxxx and an additional test for date prior to a specified date. For action, move to trash, NOT delete. Then, if you made a mistake, you can retrieve from trash. after creating filter, there will be an open row at bottom where you can specify a folder, such as inbox, and a button to run the filter.