I can't enter my world from an older version

I have such a problem that when, due to inattention, I upgraded my server to a newer version, I could not switch to the old one, because it was written that when switching to this version, the world would be deleted. it was also suggested to create a backup copy of the world. I did it. But the problem is that a copy has already been made in the new version, and when I download it, I am still in the new version. I can't switch to the old version with my world saved. Please tell me if this can be fixed. (I am from Russia and I am writing from a translator, I apologize in advance for possible mistakes)