There are some tools out there, like the Bot Migration Wizard and the File Conversion Package for Office files (Bot Store). But honestly, with that level of disparity between versions I would suggest considering taking the time to do a proper re-write. So much has changed between those version you will likely find faster, more efficient ways to complete tasks than those available when it was first written. You may find a simple migration still leaves you with a bot that isn’t performing as well as it could be.