Smashed screen - WhatsApp retention

I hope this isn't too convoluted. The screen of my iphone 7 plus smashed last week and wouldn't recognise my touch to unlock it. That's when I realised how stupid I was for not having iCloud back up, or voice recognition as another way to unlock it. The main thing I was devastated about was the possibility I'd lost years of whatsapp messages with my brother who died suddenly in May. All the ways of unlocking it I looked up said the data would be erased. So I got a new phone, a refurbished samsung because I'd only bought the refurbished iPhone in February this year and figured a) that it was nearing the end of it's time for receiving updates, and b) getting the screen fixed would cost more than getting a newer model samsung with more features.

I thought connecting to my WhatsApp account under the same phone number would restore all the messages. However, it didn't because it asked to connect to my phone which I couldn't do, so WhatsApp installed on the Samsung completely blank - clean slate. I've also since learned you can install WhatsApp on your desktop and that would have retained my brother's messages (I think)?

Upshot is, I'm wondering if I get the smashed screen fixed on the iPhone, insert the sim (same one) and open WhatsApp, will the message history still be there or will it have erased there too?

Any advice or suggestions hugely welcomed.

Thanks,

Paula