New iPhone transfer of data

Hello

I recently bought a new iPhone and wanted to transfer data from old to new device. My old device is also an iPhone. I set up my new device and restored it with data from old, but I didn’t realise a recent back up of old device had not been done. So my new device now has only data up to April this year and nothing after. I’ve done a recent back up of old device and now want to transfer over new data to new device. How do I go about doing this? I read online to “erase all content and settings” if I do this, it won’t erase my data on my old device will it? I’m so inept with tech!

thanks in advance!