Just found out that 1 writer does the job it works with my Orbit reader ETC.
However according to the introduction it can save into Dropbox so I linked it to my account but I can't work out which format it saves in does it save to text automatically or do I have to export it and if so what do I do to get it and can I read it on windows?
By Chantal Hampson, 10 November, 2019
iOS and iPadOS
One Writer Answers
From the description of One Writer it says export it to plain text or PDF from what I can see. There may be other options but as I don't have the app I don't know for sure. May be checking this one out, however.
The files it natively reads
The files it natively reads and writes are text files, so you shouldn't have any problem there.
About the only thing you'll need to be a bit careful of if you're editing files between Windows and iOS are line endings, since Windows and iOS are different. I don't have a Windows machine to test what happens if you edit a file on Windows then try to load it in oneWriter, unfortunately.