What should I do before deleting old iPhone backups?

I recently got a new phone but I transferred all my information and everything from a different phone but it is saying I need to back up the phone I have currently and I was going to delete the old phone from my back ups but it says there is 0GB backed up on this phone and the other phone has all my data

I am just wondering if I do delete the other backup phone from my current device will I lose all my data and photos ect. From my current phone?

Also my current iPhone is not backed up due to my old phone taking up all the iPhone storage

[Re-Titled by Moderator]