If you want to backup your personal files - documents, pictures, music, spreadsheets, videos, etc. - the easy way to do that is to buy or borrow a portable hard drive or a USB flash drive, then copy your files from the old computer to the portable drive and move them from the portable drive to the same folders in your new computer. It's kind of tedious, but it puts you in control, rather than relying on software.
If you want to use software, I very much recommend a proper backup app rather than Microsoft's own Windows Backup or OneDrive. A backup app will do the same thing as above, but in a more automated way, so it will be less tedious.
Your personal files are really the only thing you can backup and transfer to the new computer. You really can't backup your settings and apps. Settings need to be re-done and apps need to be reinstalled. If instead you try to move those, you will certainly experience trouble now and in the future. In any case, a new computer is a great opportunity to setup a computer all over again, with the benefit of everything you've learned up to now.
Of course, anything you have stored online doesn't need to be backed up, because it's not on your computer.
Important - this is the big 'gotcha' - if you are syncing your computer to your OneDrive you need to disable syncing on the old computer and the new computer before you start copying and moving your files.
Enjoy that new computer!