The error is saying that the importer cannot find MediaWiki's 'page' table based on the information you provided in vault/core/controller/import/config/vw.php. Make sure the correct database is named as a source. If there is a table prefix on your MediaWiki dump, make sure to specify it. If the information is correct, make sure the source is actually turned on (the 'on' field).
If your MediaWiki installation really has no page table, then it is a really old version of MediaWiki (1.4 or lower) that our importer does not support. Update to a newer version of MediaWiki before dumping.
The config file lets you specify which namespaces should be imported (near the bottom of the config file). If you set it appropriately, you should not have any empty spaces after the import.
For VaultWiki to import your MediaWiki images, your old wiki's image data directory must first be placed on the same server as your VaultWiki installation. If your wiki image directory is currently on a different server, you must access that server via FTP or your preferred means, download the directory in full, and upload it to a location of your choosing on the new wiki server. Then you must specify the correct local path to the image-data directory in the config file.