Hello again @IDriver,
I'll post the Save Editing section down below for you and you can check if there is any guide that will help you with that trailer. But like people above me said, you will have to wait for the new update 1.37 where you can buy food tank trailer, that's very similar to the one you posted above.
And if you want to play the multiplayer right now, you will have to downgrade to version 1.36 that's still supported or wait for the new update. Nobody knows when it would be, but I saw a tweet where they said it would be this week if everything goes as planned. I'll leave a guide for you down below on how to downgrade the game if you are interested.
The trailer is allowed, but you can't own it. That means you can still find it in company contracts, WoT contracts, etc., but you can't buy it from the Trailer purchase.
But if you have the new version 1.37 you can still enter the singleplayer and play it.
https://forum.truckersmp.com/index.php?/forum/423-save-editing/
https://truckersmp.com/knowledge-base/article/26
Hope my answer helps.
Have a great day.