I need to double my word count :0

I finished my first draft of a story recently and now it’s in the box waiting for 30 days to be over so I can read it over. Thing is it’s only 30K words when I want it to be more like 60-70K…

I would just accept it as a novella if that’s what it wanted to be, but even when I read through it now without a break, I can tell my plot moves too fast. I’ve added, like, the scenes I need to drive the plot forward properly and that’s it. I have no scenes that are just for character development, I have no side plot, etc…

Thing is, I just don’t know how to add these things. Where, or how, or what—i’m scared of just adding random scenes that meander around for no reason and delay the actual story.

Maybe I sound silly and you’re all gonna be like ‘just do it’, but I was wondering if anyone else struggles with this kind of underwriting and how they fix it?