They left their (valuable) junk on our land and will not take it -Michigan

So in the summer of 2022, a friend of ours was going through a divorce and was awarded some vehicles (none of which run) and trailers full of parts, scrap, and other miscellaneous items. There are a total of 4 non functional vehicles. We will call the friend "Adam" and his current girlfriend "Eve".

Adam and Eve were looking for a house during the time he was awarded the belongings, and he had nowhere to store the stuff. We offered to let them store the stuff at our home (5 acres in a rural area). The deal was that they needed to remove the belongings once they secured housing.

Adam and Eve were able to purchase and move into their home in January 2023. Their new home has comparable acreage and is also in an even more rural area than our home. My husband has asked many times over the last 12 months for them to come and get their stuff. (Unfortunately, he communicates via phone call or snapchat. This is important)

In July, we were trying to get our yard cleaned up to host a party, and my husband asked again for them to remove their stuff. Eve told him she didn't want "all that junk cluttering her yard." Some of the junk includes about 70-80 plastic pallets, and my husband found someone on marketplace looking for just that. Once he commented on the post, Eve responded publicly that my husband had zero authority to sell those as they belonged to her.

It is now December, the end of December. Guess what is still sitting in my yard? Yep. EVERYTHING they brought over. In over 18 months, they haven't even attempted to remove a single item from our property.

What exactly can I do with their stuff? I don't have the means to move it myself as it would require a tow truck capable of hauling a tow truck or two. There also happens to be a very old Volkswagen bus. I've had so many people stop in offering to buy it out of nowhere, so I know it has a bit of value attached to it. Needless to say, I don't want to just give away anything that could have some value to it. But I'm at a loss.

Since he communicated it over snap and phone, I have no paper trail to prove to the court we have literally begged them to take their stuff. We also can't prove that they have blatantly refused to remove it (her comment about cluttering her yard).

In short: how do I legally go about selling the vehicles that have been abandoned on my property for over a year?

Edit to note: we never charged them rent for keeping the suff here, nor did they EVER live with us.