Good morning,
You can update Qiime using the console, without having to download a new VM image. Inside the virtualbox image, you can install the newest version of qiime by following the instructions here: Natively installing QIIME 2 — QIIME 2 2018.2.0 documentation
Your operating system on the VM is Linux (64-bit).
Let me know if you have any questions about installing / updating qiime on the virtualbox.
Colin