Assuming Hassio.
Load the latest image. Then you can up/downgrade to any version using this command in the hassio CLI (SSH console, i.e add the SSH addon first):
hassio homeassistant update --version=x.y.z
Then copy your config files across ( add the SAMBA addon if you don’t want to do this via the CLI).
Then get yourself up to date by reading the breaking changes in each release since then. Amend your config as required and update (one version at a time if needs be).
Then automate snapshots and copying them off the SD card regularly. Search the forums for ways to do this. There’s a popular way to send them to Google Drive.