Convert 32 bit app to 64 bit app ourselves

Hello,
I'm running into an issue where I & many other people have paid over $300 for a logging software that replaces a book log & tons of math which was supposed to a one time purchase. Now the developer decided to create a upgrade that is a $99 subscription service a year & locked out all our logs in an upgrade that is a new version & 64 bit compatible. Many of us are going back to books, some are paying the $99 & I am trying to find out if we can convert the older software ourselves to 64 bit. In the end, I see either remaining iOS 10 or migrating to books again given the developer's change of heart. I would appreciate any info.