Easy is subjective.
I'd use rsync.
Code:
sudo rsync -avz {SOURCE} {TARGET}
Both the source and target file systems must be mounted.
Code:
NAME FSTYPE SIZE FSUSED LABEL UUID MOUNTPOINT
sda 931.5G
├─sda1 │ vfat 499M 54.2M ESP EEDC-1691 /boot/efi
├─sda3 │ ntfs 442.7G 36.7G OS 2E38DFD638DF9B63 /media/wil
├─sda5 │ ext4 196.1G 2e8a4205-058b-44bc-810a-910260e478f3
└─sda6 ext4 291.7G 11.8G 1aceb469-c683-41a0-81e3-ede8fe0ff4b4 /
So, which is the SOURCE and which is the TARGET? You'll need to mount sda5 somewhere - I'd put it somewhere temporary, like /mnt/a5 (mkdir /mnt/a5) first. Then I'd carefully decide what I want to copy from there. rsync is a tool for copying files.
OR you can be smarter and turn sda5 into the /home/ for the computer. You'll just modify the fstab to add it there, but there are some details that need to be handled, like deleting the old files you don't want, moving the stuff you do want to the correct relative location (moves are instantaneous inside the same file system) and you'll likely want to clean-up or merge any new files on sda6 in the HOME there. Of course, permissions need to be maintained too. There are lots of How-To guides for moving HOME directories to a different partition. https://www.howtogeek.com/442101/how...er-hard-drive/ is one. The overview is to add the new storage/partition/file system to where you need it to appear in the storage layout. This is really easy, since in Linux, we can mount file systems exactly where we need them - no "drive letters".
I'd show examples, but that might just confuse you. Skim that HowToGeek article and see if that is something you'd understand and can do. "Easy" is subjective. Only you can decide.
There are other techniques to add large areas of storage for use to a system as well. They leverage symbolic links. Lots and lots of people here use them to make storage that happens to be mounted elsewhere seem to be part of their HOME. Remember, the OS doesn't care were data is actually stored. It just wants it to APPEAR to be where it is expected. Symbolic links can make storage "appear" to be in the expected location. https://en.wikipedia.org/wiki/Symbolic_link Unix has had symlinks for many, many, decades. Linux has this same type. There is also a "hard link", but that's different and typically used in Unix/Linux versioned backups - Back-In-Time - uses hardlinks, for example. Anyway, I think Oldfred uses this technique for making extra storage easily available but appears to be in a HOME directory.
