Hi Suzie, i went through same experiance at firs, but then decided to keep control of backups muchmre seriously because multiple backups can chew up your memory very quickly no matter how large your hard drive.
This is what i have done,as you know you have an ST3 folder on your devices, i have created a new folder called ST3 Backups , this is where i keep all my backups including the data backups, and i have decided to only have one backup of both Full and database backups, this ensures i dont use up my disk space unnecessarily, so when i make a latest backup i label it in this way FULL BACKUP 13032022 , DATA BACKUP 13032022, now this gives me an easy way to find older backups and delete them and i know exactly where all my backups are, the other big advantage is i can now just AIR DROP this ST3 BACKUPS folder to my other devices knowing both my full and data backups get instantly transfered to my iphone, then when you get the prompt you overwrite the old ST3 BACKUPS folder and presto you have both devices in sync you just need to go to your iphone ST3 and load the new backups.
This insures you can stay in sync with both devices and dont create unnecessary or hard to find backups on your devices plus the big advatage is if your ST3 crashes and you need to reload it the backups are not deleted, they are in a safe folder outside ST3 software control.
I hope this helps.
So my suggestion to you is create this system first create new backups to this folder then hunt down all other backups on the device and delete them then find your bin and empy it othewise you will not gain any new disk space.
Cheers Damir