Hi @lacris
You do not nee to first update to 2.4.8-3, you can directly upgrade to 3.1.1-4.
S. this document on the upgrade procedure: ojs/UPGRADE at ojs-3_1_1-4 · pkp/ojs · GitHub (If possible, please use the command-line for DB upgrade).
Do not forget to backup everything from your OJS 2 installation!!! – you might need to reconstruct it again.
One thing that crosses my mind that you should consider before starting the upgrade: Do you have supplementary files? – The supplementary files will be migrated as galleys in OJS 3 and thus they will be visible and light accessible for the users/readers. If this is not what you want, there is a patch that you should apply to the OJS 3.1.1-4 code before starting the upgrade, that will migrate the supplementary files as submission files: pkp/pkp-lib#3016 patch not to migrate supp files as galleys but as su… by bozana · Pull Request #2021 · pkp/ojs · GitHub.
Else, note/analyse every output line when doing the command-line DB upgrade – it can contain errors or warnings, that you would need to fix in order to successfully upgrade your installation.
A suggestion: it is good to do and test the upgrade first in an test environment e.g. a test server/installation. Note every step you make. First when you checked that everything in your journal is fine, do the upgrade in production, considering all steps you have noted/taken during the test upgrade.
Best,
Bozana