You can find your world files at this location on Windows
Paste this path into the "File Name" section of the window that appears when you choose your DB and FWL files and you should see all of your single player worlds.
Please remember that you must have both files, and that they must be for the same world. You can safely ignore any .db.old and .fwl.old files, they are not needed.
You can find your local V Rising save files at this location
From this path, open the folder with your unique GUID (it will look something like e44b2230-54eb-4e1d-975c-cddd5eab4069) and inside you should see numbered AutoSave files. Select the most recent one (for example AutoSave_99.save) and upload it.
You can also follow these instructions to upload a save from another server host, just use the most recent AutoSave file you would like to upload.