I need a plugin to assign random wordpress posts to categories and random interlinker

So basically I generated around 100.000 posts but forgot to assign them to categories. Is there any wordpress plugin that can do that? It doesn't have to be a specific category, but I don't want to leave those pages orphaned as it might affect SEO.

Also, can someone recommand a plugin than can interlink them? I would have to be random, I tried link whisper and it's really slow.

Thanks

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need help about generate post? looking for solution