You can. If you followed the instructions sda2 is your new Mint install, your mounted 'file system', your new 'home' folder, 'Desktop', 'Downloads', all this is now your sda2 partition. As you can see when you look at sda2 in your Gparted screen shot, a fresh Mint install takes just over 5GB of space, your old Ubuntu had occupied about 8.5GB.I can see sda2 in gparted (see attached), I can't see it in the Linux Mint filemanager
If you backed up to sda3 then this is where the backed up files should be, on the 48GB 'device'. And they are; before there was about 25GB free space and now there are only 18GB left on sda3.
Remember, the 24GB sda2 partition does not only hold your Mint system but also Mint's 'home' folder (and not only a link), so if you allow 10GB for the system you shouldn't let Mint's 'home' folder grow much bigger than 10GB or you might run short of space on sda2. Ideally, put a new folder in Mint's home folder '2ndHomeOnSDA3', link that to 'gary' on sda3 and use that for bigger files.
Anyway, well done, glad it worked out well, all the best.