Copy them on to a SD card and get a reader like this to transfer them to the phone. I use that to get photos from my old digital camera SD card and install onto my iPhone. Once you have put them on the SD card you just put it in the reader and plug it into the phone and it's automatic. Only choice you have is whether to delete them from the card afterwards or leave them on there. I always delete them otherwise you will load them again next time you transfer photos. Cheaper ones are available for about a third of the price on Amazon
Or, install a free app on both called 'send anywhere'.
Or email them to yourself.
You could upload them to a photo sharing site and view/download them on your iPhone but that might be too much of a faff for you.
I use Android, but when connected with USB, it asks, do you want to charge battery, or do you want to copy files (or something), or share the internet connection. It can also synchonise contacts, calendars, and no doubt other files, via the cable.
mine is set up so it copies photos from phone to PC unless I tell it not to.
I can address the DCIM files through file mangler and delete photos or other content faster than with the phone buttons.
Some budget cables are charge-only and do not have the pins for data transfer. I bought some extra "genuine Samsung" two-metre cables that support intelligent fast charge and data transfer. They are thicker than short ones, presumably due to length and loss of signal or voltage drop or something. I use the blue USB3 ports.
mine asked me what I wanted to do the first time I connected via USB, I remember there are three options, I probably selected the one I want as default, can't remember now, but I can go into an option called something like "other connections" and tell it to do something else. But I am not an Iphone user so yours may not be the same.
Once connected with a data cable, you can address the phone through Windows "File Explorer"
I remember mine did that, the PC told me it had detected an iPhone, but then nothing happened and the phone didn't appear in the file list.
Thanks to all, I've managed it using a data transfer app called Photo Transfer App. It keeps nagging me to 'upgrade' if I want to transfer 10 or more pics, but I'm happy to transfer in smaller quantities to avoid paying extra.