Adding to the correct advice , you'll need to message the buyer, explaining that you are ending all items to relist as one for them to buy from one listing.
Make it very, very clear in your eBay message and explain what you are doing and why, ensure it's clear you are not removing the items for an off eBay sale but for the buyer to buy them from your eBay listing.
eBay read all messages going through their system, leave no room for those little bots to have any doubts the purpose for ending the items! 🙂
@apjmaac