Flixzter

So I finished my final exam and decided to continue on the SMP world with my friends. Then I found out we can change the server to a 1.17 Spigot. But after that all our things are gone. But if we change back to Paper 1.16.5 its back. So I was wondering if there's a way that we can keep all our items and things we built in the server while updating to the 1.17 spigot. Please Help!