The easiest way is to right click on the image then open the image with paint on a Windows computer .
Set the image on pixels ,put your length in 1200 and width is automatically done,
Then just save as a JPEG.
A little bit of a hassle if converting a few at one time otherwise a conversion program does them all in one go.
I was a little like AVB ,at first I didn't want a mobile or smart phone but when you do it's like 1 million times easier to get things done. There really is no excuse these days for not having a mobile unless you live somewhere there's no service , people would give me broken I phones ( password locked) but it wasn't hard to repair and install new operating systems. Just google what you don't know.
Besides not too many people have land lines these days because they are a rip off even the pay phones are free.https://exchange.telstra.com.au/why-were-making-payphones-free-for-calls-around-australia/
