@big-flag-47024 I'm going through a similar phase, pivoting my career into Product Marketing. Let me share my experience:
I work in a startup (the product is yet to hit the market, a small team of 5), and the target customers are product marketers. I report directly to the CEO who has almost 11 years of experience as a PMM. A few days after I joined as a Writer, he told me not to confine myself to the role of a writer but move into Content Marketing, and then Product Marketing (if it interests me).
Recently, I told him I'd like to be involved in Product Marketing related work, and he was more than willing to train me. So, now I'll get some experience regarding PMM works apart from creating content for the blog.
The reason I tell you all this is that the best way to get hired as a PMM from Content Marketing is by asking for the role within the company. I think it would work well in a startup because apart from positioning and messaging, PMMs are responsible for creating content for the blog until a dedicated content team is in place. I believe that would be a great start, and you can pivot from there.
A few things he told me so far:
1. Be obsessed with numbers: know what KPIs you need to track (unable to tell you more, maybe I can after a few weeks/a month). Rather than the number of deliverables, it's all about the impact they are making on the organizational level revenue and growth goals.
2. Read more on PM-related topics/books and get some understanding
3. He gave me a brief into what's positioning and messaging, and the roles PMMs typically play in an organization (it's much better to hear from a PMM than reading from an article because you can ask doubts right away)
Of course, I'm lucky in some ways (writing for PMMs, the CEO has trained PMMs before). Still, I'd highly recommend asking within the company and making your way into, I don't know, demand-gen maybe.